Chocolate Layer Cake with Vanilla and Chocolate Custard Filling

Instructions

For the Filling:

1. In a large bowl or jar, mix together the sugar and cornstarch. Add about half of the milk and stir until the cornstarch is completely dissolved. Then, pour in the remaining milk and mix well.
2. In a separate bowl, whisk the three eggs with a fork for about 1 minute. Add the beaten eggs to the milk mixture and stir to combine.
3. Pour the mixture into a saucepan, passing it through a sieve to remove any egg membranes.
4. Stir constantly over medium heat until it begins to thicken and bubble. Reduce the heat to low and continue stirring for another 2 minutes.
5. Divide the custard equally into two bowls. Add vanilla to the first custard and sift cocoa powder over the second. Stir until well combined.
6. Cover the custards with plastic wrap in direct contact and let them cool completely at room temperature.

For the Chocolate Cake:

1. Line an 8-inch (20cm) round baking pan with parchment paper and set aside.
2. Preheat the oven to 350°F (180°C).
3. In the bowl of an electric mixer, combine the eggs and sugar. Beat at medium speed for 5 to 7 minutes or until a fluffy and light mixture forms.
4. Add the vegetable oil, milk, and yogurt. Gently stir with a wire whisk to combine.
5. Sift the flour, cocoa powder, baking powder, and salt over the mixture and gently fold until well combined and smooth. Be careful not to overmix.
6. Pour the batter into the prepared pan and bake for about 30-35 minutes or until a toothpick inserted into the center of the cake comes out clean.
7. Let it cool to room temperature.

Simple Syrup:

1. Combine water and sugar in a small saucepan and mix until dissolved. Cook over medium heat and turn off the heat as soon as the mixture starts to boil.
2. Let it cool before using.

For the Chocolate Ganache Topping:

1. In a medium bowl, combine the chocolate and heavy cream. Melt using a double boiler or microwave in 30-second intervals, stirring until smooth.
2. Add the diced butter and stir until fully incorporated. The butter will melt with the heat of the chocolate.
3. Refrigerate for 20-30 minutes, stirring occasionally, until it reaches a good spreading consistency.

Assembling the Cake:

1. Level the top of the cake and cut it into three equal layers. Place the first layer on the serving plate and moisten it with syrup.
2. Place each custard in a piping bag and cut the tip to create an opening of about 1/2 inch (1,3cm).
3. Pipe a circle of chocolate custard near the edge of the cake, then pipe another circle of vanilla custard right next to the first one, and continue creating circles with alternating colors.
4. Repeat the process, forming three layers of cake and two of filling. Reserve the remaining custards at room temperature for decoration.
5. Cover the cake with the chocolate ganache and refrigerate for about 30 minutes to set.
6. After firming, pipe the same circles with alternating colors only on the top of the cake and slide a toothpick through them to create a pattern. Pipe small dollops of chocolate custard around the cake for finishing.