Coat the chicken thighs in the Piri Piri seasoning and set aside for 10 minutes. Preheat the oven to 180°C.
Spray a large ovenproof frying pan or casserole dish with low-calorie cooking spray and place over a medium heat. Add the chicken thighs and cook for 4-5 minutes, until browned on all sides. Remove from the pan and set aside.
Spray the pan with more low-calorie cooking spray (no need to wash first), and add the onion, garlic, peppers and mushrooms. Cook for 5-8 minutes, until the onions and peppers are softening.
Add the cherry tomatoes, lemon juice and 100ml of the chicken stock. Stir, then return the chicken to the pan. Cover with a tight-fitting lid or tight-fitting kitchen foil and place in the preheated oven for 30 minutes.
Remove from the oven and add the orzo, spring onion and the remaining stock. Stir well, then return to the oven for 20 minutes, uncovered, stirring halfway through.
Stir in the chopped coriander, then taste and season with salt and black pepper if needed. Serve alone, with steamed green vegetables or an accompaniment of your choice.