Add the butter and condensed milk to a pot over medium heat. Then, add the cocoa (sifting it so that it doesn’t have any lumps).

Cook the mixture over medium heat, stirring constantly, until the mixture is thickened (about 6-10 minutes). How to tell if the mixture is thick enough: Pull the spatula through the middle of the mixture. It should take a couple of seconds for the mixture to pull back together.

Transfer the mixture to a plate (greased with butter) and let it cool down. Once it’s at room temperature (after about 20 minutes), cover it and put it in the fridge for at least 15 minutes (an hour if you want it to be easier to roll).

Set up your brigadeiros rolling station: put the chocolate sprinkles in a bowl or on a plate, get a tablespoon to measure the mixture, and get some butter to grease your hands so the brigadeiros don’t stick to your hands.

Grease your hands with some unsalted butter and then get one tablespoon at a time of the brigadeiros mixture and roll it until you form a ball.

Roll the balls in the chocolate sprinkles or other additional toppings. Refrigerate them until ready to serve (but for at least 30 minutes).