Place the chicken, peppers, onions, seasoning, salt, pepper and oil on a baking tray. Toss together to fully coat everything then bake for 20-25 minutes.
While your chicken fajita filling is cooking, make your grilled cheese. Place down a piece of bread then top with lots of cheese and the other slice of bread. Press down to flatten then butter the outsides.
Place the remaining butter in a hot pan. Melt until foaming then fry the grilled cheese on both sides until the bread is golden and the cheese is melting. Once cooked, mould over a rolling pin to create a taco case shape.
Fill your taco cases with the chicken fajita mixture and top with the extras listed in the ingredients list.