Melt 1 tablespoon of butter in a large skillet over medium-high heat. Add the chicken cubes and cook until browned on all sides, then remove the chicken from the skillet and set it aside.

Add the remaining 1 tablespoon of butter to the skillet. Sauté the chopped onion until softened, about 3-4 minutes. Stir in the minced garlic and grated ginger, cooking for another minute until fragrant.

Stir in the tomato paste, crushed tomatoes, garam masala, turmeric powder, chili powder, and salt. Bring the mixture to a simmer and cook for 5 minutes, allowing the flavors to meld.

Return the cooked chicken to the skillet. Stir in the heavy cream, sugar, and crushed fenugreek leaves. Simmer for 3-5 minutes, or until the chicken is heated through and the sauce has thickened slightly.

Serve the butter chicken hot with cooked basmati rice and garnish with fresh cilantro.