The milk should be as cold as possible; don't freeze it or anything, but make sure it hasn't been sitting out. Fill your saucepan halfway with the calculated amount of milk. Place the stove over a low, but not miniscule, flame. Note: this technique works best when performed on a gas stove, although it can be done on an electric stove, too. Preheat the electric burner to a low setting (don't let it glow red-hot), before placing the saucepan on the stove.