Vanilla Birthday Cake with Patissier Cream

Ingredients:

Cakes

• 3/4 cup butter, room temperature
• 1 and 1/3 cups sugar
• 3 large eggs at room temperature
• 2 tsp vanilla extract
• 2.5 cups of baking flour
• 1.5 tsp baking powder
• 0.5 tsp of soda
• 1/4 teaspoon salt
• 1 cup of sour milk at room temperature

Caramel custard

• 3 tablespoons of water
• 1 tbsp. + 3 tbsp. sugar
• 1 tbsp white corn syrup
• 1 cup whipping cream
• 1 cup whole milk
• Half a vanilla pod
• 3 large egg yolks
• 2 tablespoons cornstarch
• 2 tbsp (30 g) butter, cut into pieces

Frosting and assembling the cake

• 3/4 cup butter at room temperature
• 4-6 cups powdered sugar, sifted
• 6 tablespoons whole milk
• 1.5 tsp vanilla extract

Preparation:

1. Prepare the Crème Patissiere.
   
   Place the vanilla bean seeds or vanilla paste in the milk and heat until just above a boil. In a separate bowl, whisk the egg yolks, sugar, and cornstarch. Prepare a bowl with the butter by setting a sieve over it. Gradually whisk the hot milk into the egg mixture, then return everything to the saucepan. Whisk constantly (using a spatula occasionally to reach into the corners) over medium heat until the cream thickens and becomes glossy, about 2 minutes.
   
   Immediately pour the mixture through a sieve, whisking if necessary, and mix with the butter. Place a piece of plastic wrap directly on the surface of the custard, cool to room temperature, and then refrigerate until ready to use.
2. Preheat oven to 175°C. Grease two 20cm cake pans. Line the bottom of each pan with parchment paper and dust the sides with flour, shaking out any excess.
3. Bake the cakes.
   
   Using a hand mixer or a stand mixer fitted with a paddle attachment, beat the butter and sugar until fluffy, then add the eggs one at a time, beating thoroughly after each addition. Stir in the vanilla. In a separate bowl, sift flour, baking powder, soda and salt. Add the flour mixture to the butter mixture, alternating it with yogurt, starting and ending with flour and mixing well after each addition.
4. Divide the batter evenly between the two pans. Bake for 25-35 minutes, or until a tester inserted into the center comes out clean. Cool the cakes in the pans for 20 minutes, then carefully remove them to a wire rack to cool completely.
5. Prepare the caramel cream.
   
   In a medium saucepan, bring the water, sugar, and corn syrup to a full boil. Cook, uncovered and without stirring, occasionally brushing the sides of the pan with water, until the syrup turns a light amber color. Gradually whisk in the cream (be careful not to burn yourself with steam) until smooth, and cool the caramel to room temperature. Mix 1/3 cup of the caramel sauce with the pastry cream and refrigerate until ready to assemble.
6. Make buttercream icing.
   
   Using a hand mixer or a stand mixer fitted with the paddle attachment, beat the butter until fluffy. Add 2 cups of powdered sugar and start beating on low speed to incorporate, then increase the mixer speed to high until the frosting is fluffy. Stir in the milk and vanilla. Add the remaining 2 cups of powdered sugar and beat, gradually adding more, up to 6 cups, until you have a fluffy, spreadable frosting (the amount of powdered sugar will depend on the softness of the butter you started with).
7. Assemble the cake.
   
   Place the first cake layer on a plate or platter. Fill a pastry bag fitted with a simple tip with about 1 cup of frosting and pipe a ring around the edge of the cake (this will prevent frosting from leaking out). Spoon half the caramel frosting into the center of the cake and spread it evenly. Place the second cake layer on top and spread a thin layer of frosting over the top and sides of the cake.
8. Refrigerate for 20 minutes (this will coat the crumbs). Now completely cover the top and sides of the cake with frosting and smooth it out. Using a piping bag fitted with a tip of your choice, pipe frosting around the edge of the top layer. Stir the remaining caramel sauce into the remaining half of the caramel custard and spread it over the top of the cake. Refrigerate until ready to serve. The cake can be baked a day ahead and kept in the refrigerator until serving..