Heat butter and oil in a large pot, then sauté onions until golden.
Add whole spices (cumin seeds, cinnamon, cardamom, cloves, peppercorns) and cook for 30 seconds.
Stir in ginger-garlic paste, ground spices, blended tomatoes, and tomato paste. Cook until fragrant.
Add chicken pieces and salt. Sear until lightly browned and coated in spice base.
Toss in potatoes, mint, and coriander. Mix well.
Add washed rice and water. Stir gently, then bring to a simmer.
Cover and cook on low for 25–30 minutes, or until rice is fluffy and chicken is fully cooked.
Let it rest for 10 minutes before fluffing. Serve warm.