Prepare the Egg Yolk: Pinch and remove the thin membrane that keeps the egg yolk together from the egg yolk. If you find this too complicated, you can use a fine mesh sieve. Add the egg yolk to the sieve, burst it, and let it slowly drip. The membrane will be left in the sieve; discard it. You can also omit the egg yolk if you prefer.

Add the Ingredients: In a medium-sized saucepan, combine the condensed milk, egg yolk (if using), butter, and chocolate powder or cocoa powder. (tip: pass the cocoa powder through a sieve to avoid any clumping)

Cook the Mixture: Place the saucepan over medium-low heat. Cook, stirring constantly with a silicone spatula to prevent sticking. The mixture will thicken as it cooks. This usually takes about 10-15 minutes. Tip: You’ll know it’s ready when the mixture starts to pull away from the sides and bottom of the pan and you can see the bottom of the pan when you stir. Another way to test is to run the spoon through the middle; if it takes a few seconds for the mixture to come back together, it’s done.

Cool the Mixture: Pour the mixture onto a greased plate or tray to cool. I like to cover it with plastic wrap right away. Even before it cools as to prevent it from drying. Let it cool to room temperature.

Shape the Brigadeiros: Once cooled, grease your hands with butter to prevent sticking. Scoop small amounts of the mixture and roll into 1-inch balls.

Coat with Sprinkles: Roll each ball in the rainbow jimmies until fully coated. Place each brigadeiro in a small paper candy cup if desired.