Sift the flour, cocoa powder, baking powder, baking soda, and salt into a mixing bowl. Add the sugar and mix well.

Add the egg, oil, milk, and vanilla extract. Mix until smooth and well combined.

Dissolve the coffee powder in the hot water. Slowly pour the hot coffee mixture into the batter while stirring. The batter will be thin.

Grease three 6-inch round baking pans and divide the batter equally among them.

To Bake: Preheat the oven to 175°C (350°F). Bake for 20–25 minutes, or until a toothpick inserted in the center comes out clean.

To Steam: Cover each pan with aluminum foil. Place in a preheated steamer and steam over medium heat for 25–30 minutes, or until a toothpick comes out clean.

Remove the cakes from the oven or steamer and allow them to cool completely.

Make the Brigadeiro Frosting: In a saucepan, combine the condensed milk, evaporated milk, cocoa powder, and cornstarch. Stir until the powders are completely dissolved.

Cook over medium heat, stirring occasionally, until the mixture thickens.

Turn off the heat. Add the butter and vanilla extract, then stir until smooth and well combined.

Pour the warm brigadeiro frosting over the cooled cakes.

Let the frosting cool and set, then top with chocolate chips, sprinkles, chopped nuts, or your preferred topping.

Slice and serve.