Place chopped chocolate in a glass or metal bowl that can nest on top of a pot filled with a few inches of water. Bring water to a simmer, turn off heat, and then place bowl over hot water (the bottom should not touch the water). Stir frequently with a flexible spatula to encourage even melting. If necessary, remove bowl, reheat water, and replace bowl. Once chocolate is melted, remove bowl from pan, stir well, and use immediately.