Coat a large shallow pan or platter with butter or cooking spray. In a large saucepan, bring consensed milk, cocoa powder, and butter to a boil, stirring constantly with a rubber spatula. Reduce heat to medium-low and cook for 15-20 minutes, stirring constantly until mixture thickens. It should have the consistency of thick frosting.

Pour mixture into prepared pan; let cool completely and become firm (you can refrigerate it to speed up the process).

Grease your hands with butter and shape the pieces into 1 to 1 ½ inch balls. Roll each ball in sprinkles. Place on waxed paper and refrigerate for at least 1 hour before serving.