For the chicken marinade: In a bowl, combine yogurt, lemon juice, garam masala, cumin, coriander, turmeric, ginger, garlic, and salt. Add the chicken pieces and coat well. Cover and refrigerate for at least 1 hour, preferably overnight.

Preheat grill or broiler to high. Thread the chicken onto skewers and grill or broil for 5-7 minutes on each side until charred and cooked through. Set aside.

For the sauce: In a large pan, heat the butter or ghee over medium heat. Add the onions and cook until softened, about 5 minutes. Add the garlic and ginger, and cook for another minute.

Add the garam masala, cumin, coriander, turmeric, and paprika. Cook for 30 seconds until fragrant.

Add the tomato sauce and bring to a simmer. Cook for 10-15 minutes until the sauce thickens slightly.

Stir in the cream, sugar, and fenugreek leaves (if using). Simmer for another 5 minutes.

Add the grilled chicken pieces to the sauce and simmer for an additional 5 minutes to heat through.

Garnish with fresh cilantro and serve with naan bread and basmati rice.