Heat 1 tablespoon oil in a large heavy skillet over medium heat. Cook chicken until lightly browned, about 10 minutes and season with 1 teaspoon garam masala and pinch of cayenne.
Remove chicken
Heat 1 tablespoon oil in a large saucepan over medium high heat. Saute shallot and onion and garlic until soft and translucent.
Stir in butter, lemon juice, ginger, garlic powder, 1 teaspoon garam masala, chili powder, tumeric, cumin and bay leaf. Cook, stirring, for 1 minute.
Add tomato sauce, and cook for 2 minutes, stirring frequently.
Stir in half-and-half and yogurt. Reduce heat to low & simmer for 10 min
Add chicken back Season with salt pepper.
Stir cashew into the sauce. Cook for 5 to 10 minutes, or until thickened.