I love Boston cream donuts and I did have one spectacular version of this dessert at a restaurant in Chicago (Bavette’s). So it is about time I go about it myself. Traditionally a sponge cake is used for this dessert, but I get tired of sponge cakes so I am going full on moist tender buttermilk cake.
Cake taken from Baking for All Occasions, pastry cream from Flavor Flours.
1 3/4 CUPS (7 OUNCES/200 GRAMS) CAKE FLOUR
1/2 TEASPOON BAKING POWDER
1/2 TEASPOON BAKING SODA
1/4 TEASPOON SALT
2/3 CUP (5 1/2 FL OUNCES/165 ML) WELL-SHAKEN BUTTERMILK
1 TEASPOON PURE VANILLA EXTRACT
5 1/2 OUNCES (1 1/3 STICKS/155 GRAMS) UNSALTED BUTTER, AT ROOM TEMPERATURE
1 1/3 CUPS (9 1/4 OUNCES/260 GRAMS) GRANULATED SUGAR
3 LARGE EGGS, LIGHTLY BEATEN
Center a rack in the oven and preheat the oven to 350 degrees f. Butter a 9 by 2 3/4-inch round springform pan, then flour it, tapping out the excess flour. Or, lightly coat with nonstick spray and flour the pan. Line the bottom with parchment paper.
Sift together the flour, baking powder, baking soda, and salt onto a sheet of waxed paper; set aside. In a small bowl, stir together the buttermilk and vanilla; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until it is lighter in color, clings to the sides of the bowl, and has a satiny appearance, 30 to 45 seconds. Increase the speed to medium-high and add the sugar in a steady stream, stopping the mixer occasionally to scrape down the sides of the bowl. Continue to beat on medium speed until the mixture is lighter in color and fluffy, 3 to 4 minutes.
With the mixer on medium speed, add the eggs, 1 to 2 tablespoons at a time, beating after each addition until incorporated. If at any time the batter appears watery or shiny (signs of curdling), increase the speed to mediumhigh and beat until the batter is smooth again. Then return to medium speed and resume adding the eggs, beating until smooth, stopping the mixer as needed to scrape down the sides of the bowl.
On the lowest speed, add the flour mixture in three additions alternately with the buttermilk mixture in two additions, beginning and ending with the flour mixture and mixing only until incorporated after each addition. Stop the mixer after each addition to scrape down the sides of the bowl.
Bake the cake until it springs back when lightly touched in the center, a wooden toothpick inserted in the center comes out free of cake, and the sides are beginning to come away from the pan, 30 to 35 minutes. Transfer to a wire rack and let cool in the pan for 5 to 10 minutes.
Slip a small metal spatula between the still-warm cake and the pan and run the spatula carefully along the entire perimeter of the pan. Release the springform clasp and remove the sides. Invert a rack on top of the cake, invert the cake onto it, and lift off the bottom of the pan. Slowly peel off the parchment liner, turn the paper over so that the sticky side faces up, and reposition it on top of the layer. Invert another rack on top, invert the cake so it is right side up, and remove the original rack. Let cool completely.
Coffee Pastry Cream:
6 tablespoons (80 grams) sugar
2 tablespoon plus 2 teaspoon superfine white rice flour or 3 tablespoons Thai white rice flour
2 cup milk
4 large egg yolks
1.5 teaspoon pure vanilla extract
4 tsps of instant espresso
Set the strainer over a bowl near the stove. Whisk the sugar and rice flour together in a small heavy-bottomed saucepan. Whisk in about 2 tablespoons of the milk to make a smooth paste. Whisk in the egg yolks until smooth; whisk in the rest of the milk and instant espresso. Cook over medium heat, stirring constantly, sweeping the bottom, sides, and corners of the pan to prevent the mixture from scorching.
When the mixture begins to simmer, set a timer for 5 minutes and continue to cook and stir, turning down the heat if necessary to barely maintain a simmer.
Immediately scrape the custard into the strainer. Stir the custard through it, but don’t press on any bits of cooked egg that may be left behind. Scrape the custard clinging to the underside of the strainer into the bowl as well. Stir in the vanilla extract. Let cool for about half an hour, then cover with wax paper or plastic wrap pressed directly against the surface of the custard to prevent a skin from forming. Refrigerate until chilled.
4 ounces heavy or whipping cream
1 tablespoon corn syrup
4 1/2 ounces chopped dark chocolate or semisweet chocolate chips
1/2 teaspoon vanilla extract
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. Add vanilla.
Slice cake in half height-wise. Spread pastry cream on top side of bottom half. Place top half on top. Drizzle warm glaze over top.