In a saucepan over medium heat mix the condensed milk, cocoa and butter. Cook, constantly stirring with a wooden spoon for about 10-12 minutes or until thickened. You will know that is ready when you are able to see the bottom of the pan when tilting it.
Remove from the heat and carefully transfer the hot mixture to a separate greased bowl to cool. Cover you hands wit butter and roll the mixture into small balls. Roll the ball over the chocolate sprinkles until completely covered. Enjoy!
Variation: You can add to the mixture, while still warm small pieces of cookies (we like to use shortbread cookies) and serve it in a large bowl. This is called Brigadeirao, and it is an easy option as you skip all the work that making the small balls and covered them with chocolate sprinkles requires.