Dice your apple.
After you are done cooking the oatmeal, let it cool for a few minutes before stirring in your additional cinnamon, chocolate protein powder and psyllium husk powder.
Feel free to let it cool off further if you want it to thicken up more (or make the night before for a really thick oatmeal in the morning!). Eat and enjoy
The amount of liquid will depend on how thick you like it, and how absorbent your protein powder is and if you are using the psyllium husk powder. You can base it off your package (I generally add a lot more water than directed because I like really volumious oats and thicken it with the help of the above ingredients)
Don't have chocolate protein powder? Feel free to use vanilla instead (or add your vanilla with a bit of cocoa/cacao powder)