Blend all marinade ingredients except chicken into a purée using a food processor.
Coat chicken in the marinade and refrigerate for at least one hour.
Sauté sliced onion and chillies in half the butter for 10 minutes until golden.
Sear the marinated chicken in the same pan in batches over high heat for 2 minutes.
Add onion mixture, marinade, cream, and stock to the pan and simmer for 10 minutes.
Season with salt, pepper, and coriander once chicken is cooked and sauce has thickened.
Heat oil in a deep pan or fryer to 160°C.
Fry potato batons for 3 minutes until tender but not colored, then drain.
Increase oil heat to 190°C and fry chips again for 3 minutes until crisp.
Serve the hot chips alongside the chicken curry.