1) Combine first 9 ingredients and marinate overnight.

2) Heat 1 tablespoon oil in a large saucepan over medium high heat.

3) Saute onion until soft and translucent.

4) Stir in butter, lemon juice, ginger, garlic , 1 teaspoon garam masala, cumin and bay leaf. Cook, stirring, for 1 minute.

5) Add tomato sauce and diced tomatoes, and cook for 2 minutes, stirring frequently.

6) Stir in cream.

7) Reduce heat to low, and simmer for 10 minutes, stirring frequently.

8) Season with salt and pepper.

9) Remove from heat and set aside.

10) Heat 1 tablespoon oil in a large heavy skillet over medium heat.

11) Cook chicken until lightly browned, about 10 minutes.

12) Reduce heat, and season with 1 teaspoon garam masala and.

13) Stir in a few spoonfuls of sauce, and simmer until liquid has reduced, and chicken is no longer pink.

14) Stir cooked chicken into sauce.

15) Mix together cornstarch and water, then stir into the sauce.

16) Cook for 5 to 10 minutes, or until thickened.

17) Top with cilantro, if desired.