Asma Khan’s Achari Murgh

6 tbsp vegetable oil

1 large onion, halved and sliced into thin half-moons

¼ tsp fennel seeds

¼ tsp black mustard seeds

¼ tsp nigella seeds

1/8 tsp fenugreek seeds

¼ tsp whole cumin seeds

1 tsp garlic paste

1 tbsp ginger paste

1kg skinless chicken thighs on the bone

½ tsp ground turmeric

1 tsp ground coriander

¼ tsp Kashmiri red chilli powder

1kg plain yogurt

1 tsp salt, or to taste

1 fresh green chilli, slit open lengthways; plus extra, chopped,

to garnish

handful of coriander leaves, chopped, to garnish