In the same pan, melt butter. Then add onions and sauté until golden.
Add ginger paste, garlic paste, and all spices (salt, coriander powder, cumin powder, Kashmiri chili powder, garam masala, and turmeric). Sauté covered until the oil separates. You can add a splash of water to prevent burning.
Add Greek yogurt, tomato paste, diced tomatoes, almond powder, and sugar. Sauté for another 2-3 minutes.
Transfer to a blender or food processor and purée until you have a smooth paste. Return to pan.
Add heavy cream to form a creamy sauce.
Add chicken and simmer covered for about 20 minutes or until the chicken is cooked through (test a piece). If you want it to be saucier, you can add more heavy cream or milk.
Sprinkle kasuri methi on top. Enjoy with naan or rice.