Steps
1. In a medium size pan, heat the condensed milk over medium heat.
2. Add the cocoa and butter and mix until it's all blended together.
3. Reduce the heat to low and keep stirring until the mixture thickens and starts to pull away from the sides of the pan.
4. Grease a plate with butter and pour the mixture onto it.
5. Let cool for 10 minutes before cutting into cubes.
6. Roll the cubes in cocoa powder or chocolate sprinkles and serve.