01 -
Combine the condensed milk, chocolate pieces, and butter in a bowl safe for microwave use.
02 -
Pop it in for 30 seconds on medium-high. Take it out and give it a good stir. Keep going with 30-second bursts, stirring after each, until your chocolate's fully melted and everything looks smooth and mixed.
03 -
If you prefer, empty the condensed milk into a sturdy, medium saucepan. Toss in the chocolate and butter.
04 -
Warm it up on low-medium heat, stirring all the time, until butter and chocolate completely melt and mix together. Don't turn up the heat too high or your sauce might get grainy.