Heat 1 tbsp of rapeseed oil in a deep non-stick pan over a medium heat. Add the onion and cook for 4-5 minutes until softened and translucent.
Add the garlic and cook for a further 2-3 minutes until softened.
Add the chicken and cook for 4-5 minutes, to seal.
Add the garam masala and cook for 1 minute.
Stir in the peanut butter, coconut milk and tomato passata. Bring to the boil, then immediately reduce to a simmer.
Continue to cook for 30 minutes - at a simmer - until the sauce ahs reduced and thickened to a desirable consistency, and the chicken is cooked through.
Serve with basmati rice, garnished with a scattering of salted peanuts.