Deluxe Boston Cream Pie

I made this cake a really long time ago - like last summer for my birthday. I never posted about it because I didn't extremely love it. But photos of the cake have been sitting and waiting for their turn, and looking back on my recipe notes I see that I wrote that the vanilla diplomat cream filling was super yummy, and the cake overall was good - I'm just really nitpicky! I think I was disappointed because I didn't really like the buttermilk cake, but then it was the spongey kind and as I've said a million times, I prefer dense cakes. Though I think this style of cake is just the way it's supposed to be for a boston cream pie, because that's what it was like when I made one of my first Daring Bakers' challenges bostini cream pie. So maybe it's just me, and not the cake. I would make this cake again but with a different buttermilk cake, use less filling (it oozed out and the top layer of the cake slid off, yikes), and use less whipped cream frosting.

I haven't made anything else from Baking for All Occasions - any recommendations?

If this sounds good, you might also like:
Orange Chocolate Chunk Cake
Lemon Lust Cake
Strawberry Cream Cake
Tiramisu Cake

Deluxe Boston Cream Pie
Adapted from Baking for All Occasions

Buttermilk Cake
1 3/4 cups (200 grams) cake flour
1/2 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
2/3 cup (165 mL) well-shaken buttermilk
1 tsp pure vanilla extract
5 1/2 ounces (1 1/3 sticks) unsalted butter, at room temperature
1 1/3 cups granulated sugar
3 large eggs, lightly beaten

Vanilla Diplomat Cream Filling
1 cup whole milk
1/2 cup granulated sugar
1 tsp vanilla extract
3 large egg yolks
3 tbsp all purpose flour
2 tbsp unsalted butter

2/3 cup heavy cream
1 tsp vanilla extract
1 tsp dark rum

Whipped Cream Frosting and Dark Chocolate Glaze
2 cups heavy cream
10 ounces semisweet chocolate, finely chopped

To make the buttermilk cake:
Center a rack in the oven and preheat the oven to 350F. 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; 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, cling sot 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 colour 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 medium-high 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.

Pour the batter into the prepared pan. With the rubber spatula, spread the batter form the center outward, creating a slightly raised ridge around the outside rim.

Bake the cake until it springs back when lightly touche din the center, a wooden toothpick inserted in the center comes out free of cake, and the sides are beginning to come away form 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 claps and remove the sides. Transfer cake to cooling rack. Let cool completely.

To make the vanilla diplomat cream filling:
Rest a fine-mesh sieve over a 1 quart bowl and set nearby for straining the pastry cream later. Pour the milk and 1/4 cup of the sugar into a 1 1/2 quart saucepan. Add the vanilla.

In a small bowl, whisk the egg yolks until blended, then whisk in the remaining 1/4 cup sugar. Add the flour and whisk to combine; set aside. Bring the milk mixture just to a boil over medium heat. Remove from the heat and pour half of the milk mixture into the yolk mixture while whisking constantly. Return the combined mixture to the saucepan and whisk to combine. Return to medium heat and heat, stirring constantly, until the mixture just comes to a boil, 1 to 2 minutes. It will have thickened at this point. Continue to stir and simmer until it is smooth and thick, about 1 minute more. Remove from the heat, add the butter, and stir until the butter is melted and incorporated. Pour through the sieve into the bowl. Set aside to cool for 15 to 20 minutes. (Once it has cooled, you can refrigerate it in a sealed container for up to 3 days.)

To assemble the dessert:
In a medium, deep bowl, using a whisk or a handheld mixer, whip the heavy cream until soft peaks form. Refrigerate briefly while splitting the cake.

Using a 12 inch serrated knife, split the cake in half horizontally. Place the bottom layer, cut side up, on your cake plate. Spoon about 1/2 cup of the whipped cream into a pastry bag fitted with a 5/16 inch plain open tip. Pipe a line of the whipped cream around the edge of the cake layer. Stir the vanilla and rum into the cold pastry cream until smooth. Then fold the remaining whipped cream into the pastry cream. Spoon the filling evenly over the cake layer. Using an offset spatula, spread it evenly just to the line of whipped cream. Center the other cake layer, cut side down, on top.

To make the whipped cream frosting and dark chocolate glaze:
In a medium deep bowl, using a whisk or handheld mixer, whip 1 cup of the cream until soft peaks form. Using a metal icing spatula, frost the top and sides of the cake with the whipped cream. Place the cake uncovered in the freezer for 40 minutes only (this is just enough time to chill the whipped cream frosting.)

While the cake is in the freezer, prepare the chocolate glaze. Put the chocolate in a medium bowl. In a small, heavy saucepan, bring the remaining 1 cup cream just to a boil over medium-low heat. Pour the hot cream over the chocolate, let stand for about 20 seconds, and then whisk until smooth and shiny. Set aside to cool to body temperature.

Take the cake out of the freezer. Pour the chocolate glaze over the cake to cover the top and sides, using the metal icing spatula to assist in spreading the glaze over the top and down the sides. Refrigerate for at least 30 minutes before serving.

To serve, dip the blade in hot water and wipe dry with a towel before each cut.