Mix the condensed milk, cocoa powder and butter together over medium heat on the stove top until the mixture starts to show the bottom of the pan when you stir it (around 8 minutes)
Spread mixture out until a greased plate and let cool in fridge until coolish to the touch.
Grease hands to prevent mixture from sticking
Roll into a little ball about the size of a large grape and then roll in sprinkle. Place in mini muffin cups (or on a plate)
Recipe by Roasted at http://www.roastedmontreal.com/2014/06/easiest-sweet-ever-brigadeiros.html