It is also so totally easy that my children love to make it for their teachers and they can pretty much do it all themselves. This makes about 60 ish squares (depends how large or small you cut them!)
500g Dark Chocolate
400g condensed milk (my tin was 397g?!?!)
75g unsalted butter
1/2 tsp vanilla extract
Melt all the ingredients except the vanilla.
Take off the heat.
Add the extract.
Tip in to either square baker or medium bar pan.
Chill for at least 2 hrs.
Cut into squares and eat! (or wrap and give away)