Coat the chicken with lemon juice, Kashmiri chili powder, and salt, then cover and rest it for 20 minutes. The first seasoning should lightly stain the chicken red and begin to cling to its surface.

Mix in the Greek yogurt, kasuri methi, oil, turmeric, ginger garlic paste, coriander powder, cumin powder, and garam masala, then refrigerate for at least 30 minutes or overnight. The finished marinade should look thick and cohesive, not watery or loose.

If using onion, cook it in 1 tablespoon oil for 7 minutes until lightly golden, then let it cool. The onion should soften and sweeten without becoming deeply browned.

Blend the tomatoes, cooled onion, cashews, and water until completely smooth. The puree should have no obvious cashew pieces; blend the cashews separately with water if your blender needs help.

Melt butter in a pan and sizzle the cinnamon, cloves, and cardamom, then add ginger garlic paste and green chilies over low heat for 1 to 2 minutes. The paste should smell fragrant and cooked through while remaining pale enough that it has not scorched.

Take the pan off the heat, stir in the chili powder, garam masala, cumin, and coriander powder, then add the tomato-cashew puree. Removing the pan briefly keeps the ground spices from burning on contact with the butter.

Partially cover the pan, bring the puree to a boil over medium-high heat, then cook it over low to medium heat until thickened, stirring now and then. The mixture should lose its raw tomato smell and look darker, thicker, and more concentrated.

Pour in the hot water and simmer for 10 minutes, then remove and discard the whole spices. Small droplets of fat rising across the gravy signal that the spices and tomato mixture have cooked properly.

Heat 1 tablespoon butter or ghee in a griddle or pan, then sear the chicken in 2 to 3 batches over medium heat, turning each batch after 2 minutes. Leave space between pieces so the marinade dries and dark blistered spots form instead of the chicken steaming.

Stop searing when the chicken is nearly cooked and the coating has dried onto the pieces. The chicken will finish cooking gently after it joins the gravy, so avoid hard, dry edges.

Add the seared chicken to the gravy, loosen it with about ½ cup more hot water only if it seems too thick, then cover and simmer for 5 to 7 minutes. The chicken should become tender and reach 165°F at its thickest point when checked with a thermometer.

Stir in salt, sugar, and kasuri methi, then adjust with more garam masala or another tablespoon butter if desired. The sauce should taste balanced, with tomato brightness supported by buttery richness rather than sweetness.

Turn off the heat and fold in the heavy cream, then finish with coriander leaves and a little cream. The gravy should look smooth and glossy, never vigorously boiling after the cream goes in.