Fry the whole spices in oil for about 20 seconds. Then add the onion and cook for about 5 minutes until softened.
Stir in the ginger and garlic, then the powdered spices (except garam masala), then the tomatoes. Cook for about 10 minutes.
Add the chicken and brown for a few minutes. Add the peppers if you're using them. Then cover with water, bring to the boil then lower the heat to a simmer. Cook for about 20-25 minutes.
Stir in the garam masala at the end. Serve with rice.
Notes
Nutritional information is approximate and a guideline only.