Lady Finger Trifle (Pastry Cream)

1. Pour 2 cups of whole milk and half the sugar into a pan and bring it to a simmer over medium heat.
2. In a separate mixing bowl, add the 4 egg yolks, the remaining half of the sugar, and 1/4 cup of cornstarch. Mix thoroughly.
3. Once the milk has simmered, take half of the hot milk and slowly pour it into the egg mixture, whisking consistently to temper the eggs and prevent them from cooking.
4. Pour the tempered egg mixture back into the pan with the remaining milk and return it to medium heat. Stir consistently until the mixture thickens up to a custard-like consistency.
5. Remove the pan from the heat and add 1 tablespoon of unsalted butter and 1 tablespoon of vanilla extract, stirring until the butter melts and is fully incorporated.
6. Let the pastry cream cool down completely before assembling the trifle.
7. To assemble the trifle, create layers of cooled pastry cream and lady fingers (presumably soaked in instant coffee, given the ingredient list), topping the final layer with some cocoa powder.