Peel the apple, then grate it into a small bowl. Heat the milk. Once it's steaming add the oatmeal and stir until it's gotten a bit firm (the finer your oatmeal the quicker it will get firm and sticky, so if you're in a hurry you can put your oatmeal into a blender and shred it).
Then add the apple and the cinnamon and stir for another 3 minutes or until you're happy with the consistency. Nowi it's ready to serve. Best with raspberries or apricots.