Peanut Butter and Bacon: 2013

Published March 1, 2011. From Cook's Illustrated.

Why this recipe works:
A hot-milk sponge cake made a good base in our Boston Cream Pie recipe because it didn’t require any finicky folding or separating of eggs. Baking the batter in two pans eliminated the need to slice a single cake horizontally before adding the...(more)

Serves 8 to 10

Chill the assembled cake for at least 3 hours to make it easy to cut and serve.

Ingredients

Pastry Cream
2 cups half-and-half
6 large egg yolks
1/2 cup (3 1/2 ounces) sugar
pinch table salt
1/4 cup unbleached all-purpose flour
4 tablespoons cold unsalted butter, cut into four pieces
1 1/2 teaspoons vanilla extract
Cake
1 1/2 cups (7 1/2 ounces) unbleached all-purpose flour
1 1/2 teaspoons baking powder
3/4 teaspoon table salt
3/4 cup whole milk
6 tablespoons (3/4 stick) unsalted butter
1 1/2 teaspoons vanilla extract
3 large eggs
1 1/2 cups (10 1/2 ounces) sugar
Glaze
1/2 cup heavy cream
2 tablespoons light corn syrup
4 ounces bittersweet chocolate, chopped fine

Instructions

1. For the Pastry Cream: Heat half-and-half in medium saucepan over medium heat until just simmering. Meanwhile, whisk yolks, sugar, and salt in medium bowl until smooth. Add flour to yolk mixture and whisk until incorporated. Remove half-and-half from heat and, whisking constantly, slowly add ½ cup to yolk mixture to temper. Whisking constantly, return tempered yolk mixture to half-and-half in saucepan.
2. Return saucepan to medium heat and cook, whisking constantly, until mixture thickens slightly, about 1 minute. Reduce heat to medium-low and continue to simmer, whisking constantly, 8 minutes.
3. Increase heat to medium and cook, whisking vigorously, until bubbles burst on surface, 1 to 2 minutes. Remove saucepan from heat; whisk in butter and vanilla until butter is melted and incorporated. Strain pastry cream through fine-mesh strainer set over medium bowl. Press lightly greased parchment paper directly on surface and refrigerate until set, at least 2 hours and up to 24 hours.
4. For the Cake: Adjust oven rack to middle position and heat oven to 325 degrees. Lightly grease two 9-inch round cake pans with nonstick cooking spray and line with parchment. Whisk flour, baking powder, and salt together in medium bowl. Heat milk and butter in small saucepan over low heat until butter is melted. Remove from heat, add vanilla, and cover to keep warm.
5. In stand mixer fitted with whisk attachment, whip eggs and sugar at high speed until light and airy, about 5 minutes. Remove mixer bowl from stand. Add hot milk mixture and whisk by hand until incorporated. Add dry ingredients and whisk until incorporated.
6. Working quickly, divide batter evenly between prepared pans. Bake until tops are light brown and toothpick inserted in center of cakes comes out clean, 20 to 22 minutes.
7. Transfer cakes to wire rack and cool -completely in pan, about 2 hours. Run small plastic knife around edge of pans, then invert cakes onto wire rack. Carefully remove parchment, then reinvert cakes.
8. To Assemble: Place one cake round on large plate. Whisk pastry cream briefly, then spoon onto center of cake. Using offset spatula, spread evenly to cake edge. Place second layer on pastry cream, bottom side up, making sure layers line up properly. Press lightly on top of cake to level. Refrigerate cake while preparing glaze.
9. For the Glaze: Bring cream and corn syrup to simmer in small saucepan over medium heat. Remove from heat and add chocolate. Whisk gently until smooth, 30 seconds. Let stand, whisking occasionally, until thickened slightly, about 5 minutes.
10. Pour glaze onto center of cake. Use offset spatula to spread glaze to edge of cake, letting excess drip decoratively down sides. Chill finished cake 3 hours before slicing. Cake may be made up to 24 hours before serving.

Step-by-Step

For the Best Pie, Ditch Tradition
We deconstructed the recipe for Boston Cream Pie invented by the Parker House hotel—and found it needed a complete overhaul.

DULL, HARD GLAZE

The original glaze dries to a hard, dull-looking shell that won’t bond with the cake. And who really wants brittle piped frosting on top?
OVERLY LEAN, SWEET CAKE
The traditional sponge cake is too lean and sweet for modern tastes. And if you don’t know what you’re doing, it will bake up flat instead of airy.
RUNNY FILLING

It’s all too easy to create a pastry cream that’s too thin, leading to a filling that dribbles down the cake.

Step-by-Step

Thickener Face-Off: Flour vs. Cornstarch
When developing the pastry cream filling for our Boston Cream Pie, too often we found that the custard, which is made by heating half-and-half with egg yolks and cornstarch, failed to thicken properly. Would flour be more reliable?
THE EXPERIMENT
We made multiple batches of pastry cream thickened with 3 tablespoons of cornstarch according to our recipe, and another set thickened with 4 tablespoons of flour (a less potent thickener than cornstarch) that we cooked longer to remove the floury taste.
THE RESULTS
The flour-thickened batches of pastry cream set up and held perfectly every time, while those containing cornstarch occasionally did not set at all or even thinned out once they had thickened.
THE EXPLANATION
When starch is heated in water, its granules absorb water, swell, and eventually burst, leaking a starch molecule called amylose that diffuses throughout the solution, trapping additional water and forming a coherent network, or gel. Because cornstarch is a pure starch, it has far more amylose than flour (which is only about 75 percent starch), giving it maximum thickening power. But its purity makes cornstarch finicky. If a custard such as pastry cream isn’t heated high enough, an enzyme in the yolks called amylase can weaken the starch gels so the custard never fully sets up. And even if it does thicken properly, overwhisking the mixture can break the bonds of the starch gels and thin it out. Flour, on the other hand, contains proteins and lipids that dilute its capacity to form starch gels, so that more of it is needed for thickening. But these non-starch components also act as binders, keeping water trapped and ensuring that a liquid not only thickens, but stays that way.