Preheat the oven to 350F/177C and line two, 8-inch (20-cm) cake pans with parchment paper. Place the sugar and butter into a mixer bowl and whisk on high speed for 3 to 4 minutes, scrapping down the sides of the mixing bowl often, until the butter if fluffy. Add the vanilla and almond extracts and the eggs, then whisk again for 3 to 4 minutes until the mixture is smooth.
Pour the milk into the cake batter without stirring, then set aside. In a separate bowl, combine the dry ingredients: almond flour, all-purpose flour, baking powder and salt. Sift the dry ingredients into the cake batter, then use a hand whisk to mix the flour in. Mix the flour for about 1 minute, just until the flour is incorporated; don't over mix the batter.
Divide the cake batter evenly between the two pans and bake in the preheated oven for 28 to 30 minutes, until the tops are golden brown and a toothpick inserted into the center comes out clean. Allow the cake layers to cool completely before assembling the cake.
While the cake layers are cooling, prepare the pastry cream needed for the German buttercream. It needs to cool before being used; this can be prepared ahead of time, too.
Assembling the Cake:
To assemble the cake, first spread a generous amount of frosting onto the first layer, then add a few handfuls of berries. Press the berries gently into the buttercream, then top with the second cake layer. Frost the top and sides of the cake, then refrigerate for at least 15 minutes. Prepare the chocolate ganache and allow it to cool down before using, otherwise it will slide off the cake.
Pour the ganache over the top and sides of the cake, then garnish with more buttercream. I use a French star tip; number 4FT. Add the remaining fruits and/or berries on top. Refrigerate the cake if not serving immediately.
Making German Buttercream:
Place the milk and flour into a medium saucepan. Whisk the flour in until no clumps remain. If using a vanilla bean, scrape out the seeds and add the seeds and pod into the milk. Cook the milk over medium-low heat for approximately 5 minutes, until the milk is steaming hot but not boiling. Remove the vanilla bean and scrap out the seeds with a knife and add the seeds to the milk, discarding the pod. Meanwhile, in a separate mixing bowl, combine the egg yolks and sugar. Whisk vigorously for 2 to 3 minutes until the mixture is thick and pale and ribbons off of the whisk. In a small ramekin, combine the cornstarch and water to create a slurry. Add the slurry to the egg yolk mixture and whisk for 30 seconds.
Once the milk is hot, slowly temper the milk into the egg yolks. Add a little at a time and whisk well after each addition. Once the two mixtures have been combined, pour the custard base back into the saucepan. Cook the mixture over medium-low heat for 5 to 7 minutes, stirring constantly with a rubber spatula. Custard is ready when it holds its shape on the back of the spatula. Avoid cooking over high heat; this can cause the custard to separate. Remove the custard from heat and add the 1/2 cup butter and vanilla extract. Whisk the butter into the hot custard until it’s completely melted. Cover the custard with plastic wrap touching the surface, to prevent a film from forming on top. Refrigerate the custard until completely cooled, then use as a filling or for the custard buttercream.
For the buttercream. first beat the softened 1 cup butter on high speed for 2 to 3 minutes until the butter is light and fluffy. Begin adding the cooled custard, a few tablespoons at a time, and whisk on medium speed after each addition. After adding the last few tablespoons, whisk for just 30 seconds. If desired, add an additional 1 cup confectioner's sugar to sweeten the frosting.
Making Chocolate Ganache:
Heat the heavy cream on the stove top or in a microwave-safe glass bowl/cup. Cream should be steaming hot but not boiling. Add the chocolate chips and allow the chips to sit for a few minutes, melting. Then, using a spoon, stir the chocolate and cream together until smooth. If not all of the chocolate chips melt, heat the glaze in microwave at 10-second intervals, stirring after each time. If glaze is too thick, add HOT heavy cream. Do not thin out the glaze with cold cream as this will cause the chocolate to seize! Allow the glaze to cool for a few minutes if it’s too hot, then pour over your cake, pouring from the center and spreading to the edges with a spatula. Alternatively, transfer the glaze into a pastry bag and drizzle down sides first, then fill center.