For the Marinade:

Combine yogurt, lemon juice, 1Tbsp garlic, 1 Tbsp ginger, 1/2 tsp salt, 1/2 tap garam masala, cumin coriander and cayenne; Set aside.

Chicken:

Pierce the chicken in several places, then transfer to large bowl. Pour Marinade over chicken; toss to coat. Cover chicken and refrigerate at least 1 hour or overnight.

Chicken Preparation:

1)Pre-heat broiler with rack 6-8 inches from the heating element.

2)Remove chicken from bowl; discard marinade. Transfer chicken to a broiler pan, broil 8 minutes on flesh side. Remove chicken from broiler; transfer to 4-6 quart slow cooker.

For the Sauce:

1)Heat 1Tbsp oil in a large skillet over medium-high heat.

2)Add Onion and cook until just beginning to brown, 5 minutes.

3)Add 2 tsp garam masala, 1 1/2 tsp garlic, 1 1/2 tsp ginger, and Serrano; cook until fragrant, 1 minute. Stir in tomato paste; cook 1 minute.

4)Deglaze pan with tomatoes scraping up any browned bits on the bottom of pan. Transfer mixture to slow cooker; stir to coat.

Slow Cooker:

1)Cover slow cooker and cook on low-heat setting until tender, 3 hours.

2)When done transfer chicken to serving platter.

Final Steps to Sauce:

Whisk Cream into sauce; season with salt and black pepper. Pour sauce over the chicken and garnish with chopped cilantro.