On the stove top, I recommend heating on low and gradually bringing the milk to 60 degrees celsius (140 Fahrenheit). A little lower is okay, but no hotter. If you don't have a cooking thermometer, heat the milk until little bubbles form around the edge, but don't let the milk boil. Stir continuously to make sure it doesn't burn and mix until the gelatine has dissolved. From there, you can continue the steps as usual.