Cut the head off the red pepper and clear out the seeds, peel the onion, put on a baking tray and put on the bottom shelf of the oven.
Get the chicken, slice into the centre of the breast from top to bottom so it's sort of like a hole in the chicken, ready to get stuffed! Season the breasts with salt and pepper.
Get some aluminium foil, make two pieces big enough to wrap each chicken breast and place a chicken breast on each nearer the end closest to you. Open up the breast and put in the grated cheese, chilli and a few leaves of spinach. Now wrap the chicken breast in the foil, and do the same for the other one. Put the packets on a baking tray.
Bake on the middle shelf. After 20 minutes, place washed spinach leaves in the tray with the pepper and onion, pour some olive oil over and sprinkle with salt and pepper.
After 10 minutes remove the tray of vegetables and slice the pepper and onion into quarters. Put 2 pieces of pepper on each plate; fill the pieces with spinach. Take out the chicken breasts, unwrap the foil and cut each breast in half diagonally, then place half of each chicken on top of the spinach. Add the onion on top, get the tray that has the spinach, pepper, onion on and pour the juices over the dish. Voila!