Heat the butter into a pan in medium heat (400F).
When it melts, add the chocolate and the condensed milk. Stir non-stop.
Turn of the oven when it's a texture that you can see the bottom of the pan when you pass the spoon.
Pour it into a plate and take it to the fridge for about 20 min or until it cools down and acquire a stiffened texture.
You can eat like that, with a spoon, or pour it into small cups. Or you can make small balls and cover it with sprinklers.
For that, you will need mini cupcakes wrappers or smaller ones that you can find in craft stores on the candy section.
Pour sprinklers into a plate
Get half-spoon of it and roll it around you hands until it forms a ball (kids LOVE to help!) PS: spread some butter in your hand so it doesn't stick
Throw the chocolate ball on the sprinklers and spin it around until it covers the whole thing.
Keep it in the fridge and enjoy it!