THE DAY BEFORE
1. Make ginger-garlic paste (more than required; freeze the rest for next time) by pureeing 1/4 cup chopped unpeeled ginger, 3/4 cup garlic cloves, and 3/8 cup water.
2. Make chili paste (more than required; freeze the rest for next time) by pureeing 1/4 cup paprika, 1/4 cup chili powder, and 1/4 cup water.
3. Make marinade. Whisk together 1 cup yogurt, 1/4 cup chili paste, 1 Tbsp ginger-garlic paste, 1 tsp garam masala, 1/4 tsp turmeric, 2 Tbsp lemon juice, 2 Tbsp mustard oil, 2 tsp salt.
4. Add 2 lbs of chopped-up chicken and refrigerate 4+ hours.
THE DAY OF
1. Cook chicken for 18-20 min at 425 degrees.
2. Puree 1 1/4 lbs tomatoes and finely chop 2 cups yellow onions.
3. In a large pot, heat 1 Tbsp canola oil and 6 Tbsp butter on medium-high ("until they shimmer").
4. Add 1/2 tsp cumin seeds.
5. Add 2 cups finely chopped onions and cook about 12 min (until dark brown).
6. Add 2 tsp ginger-garlic paste and cook 30 seconds.
7. Add pureed tomatoes and 1 tsp deggi mirch and cook 15 min, until tomato juice mostly evaporated.
8. Reduce heat to medium and add 1 Tbsp finely chopped ginger and 1/4 cup tomato paste, and cook 2 more minutes.
9. Add marinated chicken, 1 tsp salt, and 2 cups heavy cream, and simmer 5 more minutes.
10. Serve with some cilantro on top.