Chocolate Cake with Vanilla Custard Swirl

Instructions

Vanilla Custard:

1. Combine the sugar and cornstarch in a large bowl or jug and stir. Add about 1/2 cup of milk, whisk until completely dissolved, then add the remaining milk. 
2. Using a fork, whisk the eggs for about one minute, add them to the milk mixture, and whisk to combine. 
3. Pour the mixture into a large saucepan, passing it through a sieve to remove any lumps and the yolk membranes. 
4. Cook over low heat, constantly stirring for a few minutes. When the mixture starts to bubble and thicken, whisk vigorously for about one minute more to prevent lumps from forming. 
5. Immediately spread the custard in a large container and cover it with plastic wrap in direct contact. Allow it to cool to room temperature. 

Chocolate Cake:

1. Grease a 10in (25cm) removable bottom round cake pan (3in or 7cm deep) with butter or cooking spray. Set it aside. 
2. Preheat the oven to 350°F (180°C) for about 5 minutes before baking the cake. 
3. Combine the eggs and sugar in the bowl of an electric mixer fitted with the whisk attachment. Beat on medium speed for about 5 minutes until fluffy and pale yellow. 
4. Add the oil, milk, heavy cream, and vinegar. Whisk to combine. 
5. Sift the flour, cocoa powder, baking powder, and salt over the mixture. Gently stir using a wire whisk until just combined and smooth. Don’t overmix the batter. 

Assembling the Cake:

1. Pour the batter into the prepared pan. 
2. With the help of a piping bag, pipe all the cream over the cake, creating a spiral form. You can make more than one layer of custard, but always place one over the other. 
3. Bake for about 40 minutes or until a toothpick inserted into the chocolate cake comes out with just a few moist crumbs. 
4. Allow it to cool completely at room temperature, unmold the cake and serve.