Toast the coriander seeds in a dry pan
Place the garlic, turmeric, coriander seeds, chopped chillies, ginger, and 1 tbsp oil in a food processor or pestle and mortar, and blitz to a paste
Season the chicken thighs with salt and pepper
Using a sharp knife, deeply score the chicken thighs
Rub the paste into the thighs, ensuring it covers them and goes into the score cuts
Heat 1 tsp of oil in a large frying pan, over a medium-high heat
Brown the chicken on both sides, around 4 - 5 minutes a side, then set aside
Preheat your slow cooker
Add the remaining 2 tsp of oil to the pan, and cook the onion over a medium heat, until softening and turning translucent
Add the tomato and cook for 6 - 8 minutes, until soft
Place the chicken thighs in the slow cooker
Add the onion and tomatoes
Fry the whole chillies for around 30 seconds to a minute, then add to the slow cooker
Pour over the chicken stock
Cover, and cook for around 6 hours on low/auto
Before serving, add the chopped coriander, and season to taste
Serve with pilau or plain rice