Cut chicken into 1-2 inch square pieces.

In a large bowl, combine chicken, sour cream, minced garlic, salt, chili powder, cumin, curry paste, and turmeric.

Marinate in the fridge for at least 30 minutes, or overnight.

Preheat oven to 350 F (175 C).

Put chicken into a baking dish and bake for 20-25 minutes.

Set chicken aside.

In a sauté pan over medium heat, cook sliced onions with cooking oil until just glossy but not cooked.

Remove from heat.

Puree the onions and canned tomatoes in a blender until smooth.

Heat a bit of cooking oil in a large pot.

Add minced garlic and freshly grated ginger and cook for 2-3 minutes, do not brown.

Add onion/tomato puree, chili powder, chili flakes, cumin, hot Madras curry powder, curry paste, sugar and salt.

Simmer for 30 minutes until it reaches a thicker consistency.

Add chopped fresh cilantro, whipping cream, butter, and cooked chicken.

Heat for another 10 minutes.

Garnish with more cilantro and serve with basmati rice and naan.