Pop the chicken breasts in a ziplock bag and pound until pieces are about 3/4 of an inch thick.
Marinate the chicken in the mustard, mayonnaise, lemon, chilli flakes for at least 2 hours.
Add the cumin seeds to a dry, large deep pan and cook for 1 minute.
Heat the butter and oil in the same pan.
Allow the butter to sizzle a little and add the chicken breasts with the marinade. Simmer for 2 minutes.
Turn the heat down and cover with a lid. Cook on a low heat for 20 minutes. Check at 10 minutes and add some water if need be.
Season with salt and pepper. I add 1.5 tsp of each. Add chilli flakes, red onions and pepper and cover again. Cook for a further 5 minutes.
Serve with rice and vegetables.