Heat the vegetable oil in a large pan over medium heat.
Add the chopped onions and cook until they turn golden brown.
Add the minced garlic, grated ginger, and slit green chillies. Cook for another 2 minutes.
In a mortar and pestle, crush the coriander seeds and cumin seeds. Add them to the pan and cook for a minute until fragrant.
Add the turmeric powder, chilli powder, and garam masala. Stir well to combine.
Add the boneless chicken thighs to the pan and cook until they are browned on all sides.
Pour in the coconut milk and chopped tomatoes. Season with salt according to taste.
Cover the pan and let the curry simmer for 25-30 minutes, or until the chicken is cooked through and the sauce has thickened.
Garnish with fresh coriander leaves before serving.
