My Favorite Chocolate Sheet Cake

Instructions

For the Chocolate Cake:

1. Butter a 9x13in (23x33cm) baking pan and set it aside. 
2. Preheat the oven to 350°F (180°C). 
3. Combine the milk and vinegar in a small bowl. Stir until well combined and set it aside. You can use 3/4 cup (180g) of store-bought buttermilk instead. 
4. Sift the flour, cocoa powder, baking powder, baking soda, salt, and sugar into a large bowl. Stir to combine the dry ingredients. 
5. Form a well in the center; add the eggs, milk mixture (or buttermilk), vegetable oil, vanilla, and warm water. Using a wire whisk, stir until just combined. Do not overmix the batter. 
6. Pour the batter into the prepared pan and bake for about 25 to 30 minutes or until a toothpick inserted in the center comes out clean. 
7. Let the cake cool completely in the baking pan at room temperature.

For the Chocolate Topping (Brazilian Brigadeiro):

1. Place the cocoa powder and hot water in a medium bowl. Whisk until completely dissolved and smooth. 
2. Combine the sweetened condensed milk, cocoa mixture, butter, and salt in a saucepan. 
3. Cook over medium heat, stirring constantly and scraping down the sides of the pan with a silicone spatula until it bubbles and starts to thicken. Don't let it get too thick because the mixture will thicken as it cools.
4. Turn off the heat and add the chocolate. Stir until well combined. The heat of the mixture will melt the chocolate. 
5. Pour the hot mixture over the cake before it starts to set. Spread it evenly and sprinkle chocolate sprinkles on top. 
6. Let it cool completely at room temperature, cut it into squares and serve. 
7. Store the cake at room temperature or remove it from the fridge about 1 hour before serving.