Boston Cream Pie
I don’t typically wait this long to share with you James’ selection for his birthday cake, but this spring has been a busy one. We’ve got lots of gardening news to share with you in an upcoming post, but I didn’t want to let James’ birthday cake slip too far into the past before giving you a peek at the deliciousness and inviting you to have a slice for yourself.
I never put any restrictions on James’ options for birthday cakes each year, but I do make one stipulation: it must be a cake. No pies, crisps, tarts, or cupcakes. What’s wrong with cupcakes? I realize I’m in the minority, here, but I don’t think they say “birthday”. Instead, they say, “here is a tiny piece of cake mounded with frosting and surrounded with inedible paper.” No, a birthday cake should be 100% celebratory, 100% over-the-top, and 100% edible.
So, with that one filter in place, James chose to expose a gaping loophole: Boston Cream Pie. Why is it a cake that’s called a pie? This cake has identity issues! According to many baking historians, the recipe originates from Boston in the 1800s when pie pans were more common than cake pans. Essentially, it was a cake baked in pie pans and filled with pastry cream (which is usually used in tarts and other pastries). So, while it is a cake, it’s also pie-like. The name “pie” has stuck with it even though it’s now commonly baked in cake pans so that the sides are kept neat and cake-like.
Neither of us had ever actually had a slice of a real Boston Cream Pie — though we both do enjoy doughnuts of the same name and Ben & Jerry’s pint-sized rendering complete with chunks of sponge cake and a swirl of chocolate and pastry cream in every bite. In effect, this was a cake we’d only seen in photos and had only tasted in theory.
We began the birthday feast with a zesty salad recipe: Pepperoncini Chopped Salad with Romaine, Red Bell Pepper, and Feta. Rounding out his birthday feast, James also asked for Chicago-Style Deep-Dish pizza — I made one pepperoni and one Italian sausage with spinach. I may share that recipe with you, one day, but this post is getting too long already!
Method to the Madness
When you do a quick internet search for Boston Cream Pie, you find a lot of variations on what is seemingly an easy idea. Some replace the cake layers with regular yellow cake or even a boxed cake mix while others use a vanilla pudding rather than the traditional pastry cream. Though some of the recipes out there would’ve made for a slightly easier process, I had my heart set on making a version that was as authentic as possible.
Fortunately, since I was going to be making this cake without having any personal experience with the “original”, I did not have to go very far to find a reliable recipe. America’s Test Kitchen’s Baking Illustrated had a very detailed and streamlined recipe already outlined for me.
The recipe raised a few points I thought were worth highlighting, here:
Don’t skip the strainer: Even though putting the finished pastry cream through a fine-mesh sieve seems like a pointless task messing up yet another dish or two, believe me, it’s worth it. While I couldn’t see any lumps or graininess in my pastry cream, one pass through the sieve showed me my pastry cream could be even creamier. Even though you temper the eggs properly and don’t overcook the mixture, straining the cream before chilling it is worth the effort.
Don’t overbeat the whites: There are many cake recipes requiring you to beat egg whites “until stiff peaks form”. In this case, you definitely want to stop short of stiff peaks, otherwise it will be nearly impossible to fold the whites into the rest of the batter mixture without having to stir and fold so much that you deflate the batter. One reason slightly softer egg whites works for this sponge cake is because a considerable amount of air is beaten into the yolks as well.
Corn syrup in the ganache: I’m definitely not a fan of gratuitously sweetened things or artificially-enhanced foods. So, with a lot of buzz, lately, about high fructose corn syrup, you might be wondering why it’s necessary to put corn syrup in a ganache topping. First, be assured that corn syrup is not the same is high fructose corn syrup. The HFCS is highly-processed to convert dextrose into fructose, making for a very unnaturally concentrated sweetener that’s difficult for your body to digest all at once. GMO concerns aside (buy organic corn syrup if it’s available), regular corn syrup is as safe for you to eat in moderation as honey, maple syrup, or sugar. In this recipe, the corn syrup serves primarily to give the ganache the correct finished texture while simultaneously sweetening the bittersweet chocolate and cream. The end result is a satiny smooth coating that doesn’t turn into a hard, crackly shell but also doesn’t remain a dribbling mess, running off the cake completely.
Spread out the work: While it’s entirely possible you could make this recipe from start to finish in one day, why put yourself through the hassle of coordinating cooling times and messing up several pots, bowls, whisks, etc.? You’ll note the assembled cake should be served within a day, but the individual components can be made ahead. For James’ birthday, I made the pastry cream the day before so it could be chilled and completely thickened. That gave me plenty of time on the big day to make the cake, cool the layers, and do the easy bit of assembly.
Boston Cream Pie
Adapted from Baking Illustrated
2 cups half-and-half
1/2 cup granulated sugar, divided
1/8 teaspoon salt
5 large egg yolks
3 tablespoons cornstarch
4 tablespoon cold unsalted butter (cut into four pieces)
1 1/2 teaspoons vanilla paste (or vanilla extract)
1/2 cup cake flour
1/4 cup all-purpose four, plus additional for dusting pans
1 teaspoon baking powder
1/4 teaspoon salt
3 tablespoons milk
2 tablespoons unsalted butter
1/2 teaspoon vanilla extract
5 large eggs, at room temperature
3/4 cup granulated sugar, divided
1 cup heavy cream
1/4 cup corn syrup
8 ounces bittersweet chocolate, chopped into small pieces
For the pastry cream: In a medium saucepan, heat the half-and-half, 6 tablespoons of the sugar, and salt over medium heat until just simmering; stirring occasionally to dissolve the sugar. Meanwhile, in a medium bowl, whisk the egg yolks until thoroughly combined; whisk in the remaining 2 tablespoons of sugar until mixture is creamy and sugar has dissolved. Whisk in the cornstarch until combined and mixture is thickened and a pale yellow (about another 30 seconds).
When the half-and-half mixture reaches a full simmer, gradually whisk the entire mixture into the yolk mixture by pouring in a thin stream while whisking constantly to temper the eggs. Return the mixture to the saucepan; simmer over medium heat, whisking constantly, until a few bubbles burst on the surface and the mixture is thickened and glossy (about 30 seconds). Off the heat, whisk in the chilled butter and vanilla paste. Strain the pastry cream through a fine-mesh sieve set over a medium bowl. Press plastic wrap directly onto the surface of the cream to prevent a skin from forming; refrigerate at least 3 hours or up to 2 days.
For the sponge cake: Adjust an oven rack to the lower-middle position and preheat the oven to 350-degrees. Lightly butter or grease two 9-inch round cake pans; cover the bottoms with parchment rounds, lightly grease the parchment rounds, and then dust pans lightly with flour, tapping out excess.
In a medium bowl, whisk together the flour, baking powder, and salt. In a small microwavable bowl, heat the milk and butter for about 20-30 seconds in the microwave until butter melts (do not boil); add the vanilla and set aside.
Separate 3 of the eggs, placing the whites in a medium mixing bowl; reserve the 3 yolks and the remaining 2 whole eggs in a large mixing bowl. Beat the 3 whites at low speed until foamy; increase the mixer speed and gradually add 6 tablespoons of the sugar, beating until soft peaks form (do not overbeat). Add the remaining 6 tablespoons of sugar to the whole-egg mixture in the large bowl; beat at medium-high speed until eggs are very thick and a pale yellow color and sugar dissolves (about 5 minutes). Add the beaten whites to the whole-egg mixture.
Sprinkle the flour mixture over the egg mixture; fold very gently with a large rubber spatula. Pour the milk mixture into one side of the bowl. Continue folding until no trace of flour remains and the mixture is uniform.
Immediately pour the batter into the prepared cake pans, spreading to the edges with an offset spatula. Bake at 350-degrees until cake tops are light brown and spring back slightly when touched (about 15-18 minutes). Immediately run a knife or spatula around the pan perimeters to loosen cakes. Gently invert the cakes onto a flat plate or a small wire rack, remove the parchment round, reinvert the layers onto racks to cool to room temperature.
For the chocolate ganache: When the cake layers have cooled to room temperature, bring the cream and corn syrup to a full simmer in a medium saucepan over medium heat. Remove from the heat and add the chopped chocolate; cover loosely and let stand for 8 minutes. Stir the mixture until the chocolate is completely melted and mixture is smooth. If lumps of unmelted chocolate remain, place the mixture over lowest heat setting and stir constantly just until melted. To thicken the ganache for glazing, cool the mixture at room temperature until lukewarm and a spoonful drizzled back into the pan mounds slightly.
To assemble the “pie”: When the ganache is nearly cooled, place one cake layer on a cardboard round set over parchment. Carefully spoon the pastry cream onto the top of the layer, spreading evenly up to the edges, leaving about 1/2- to a 1/4-inch border. Place the second cake layer on top gently, making sure the layers’ sides line up evenly. Once aligned, press the top layer down gently to bring the pastry cream to the edges but not oozing out. Using a ladle or large spoon, pour the ganache onto the middle of the top layer, spreading in circles, eventually letting the ganache flow down the sides. If necessary, use a metal spatula to coat the sides evenly. Refrigerate the cake in a covered container until the ganache fully sets (about 1 hour). Serve the same day or preferably within a few hours.
For a dessert concept so simple — pastry cream slathered between two sponge cake layers and then covered with chocolate — this was a birthday cake so over-the-top we still refer to it fondly even weeks later! The pastry cream was decadently creamy and vanilla-y without being too sweet or runny to stay put. The sponge cake was light enough to not smash out all the pastry cream and yet imparted a nice flavor rather than being a silent partner. The ganache basically sealed the deal — cementing together both the structure and the taste of this simple yet puzzling dessert.
Here I have to admit to complete photographic failure. I was in such a hurry to slice it up and dig into a slice, that I forgot to take a photo of the finished whole cake. It would’ve been ideal to show you the finished product, right? Halfway through slicing, James asked me if I’d taken a photo… sigh how will this be a bloggable recipe now?! In my celebratory/salivatory state, I snapped this photo of a half-sliced Boston Cream Pie — I didn’t even make sure it was a good photo before continuing toward ganache-covered bliss. I am officially ashamed and will try to do better in the future, regardless of what tempting morsel is before me.
Thankfully, “birthday boy” was once again pleased with his cake selection and another memorable cake recipe has been filed into our rotation. In case you were curious, here’s a rundown of James’ birthday cakes since 2010: