Why do I need to melt butter with chocolate? When I bake with chocolate, especially for cakes and brownies, the recipes always say to melt butter along with the chocolate. Why is this? Would melting them separately cause some sort of problem?
Melting them together makes the chocolate less sticky and therefore less likely to stick to your melting pot.

Probably wouldn't cause any other problems if you did them separately; there is no chemical reaction between the chocolate and the butter. 

Either way its convenient to melt them together so that you can do it all at once and save time.