Heat vegetable oil in a large pan over medium heat.
Add chopped onions and sauté until they turn golden brown.
Stir in minced garlic, grated ginger, and slit green chillies. Cook for 2 minutes.
Add turmeric powder, coriander powder, cumin powder, and garam masala. Cook for another minute until fragrant.
Add boneless chicken thighs to the pan and cook until they are browned on all sides.
Pour in coconut milk and chopped tomatoes. Season with salt according to taste.
Cover the pan and simmer for 20-25 minutes, or until the chicken is cooked through and tender.
Garnish with chopped fresh coriander leaves before serving.
