In a dry pan, roast the cumin and coriander seeds until fragrant. Let them cool, then grind into a coarse powder. Combine with the garam masala, red chili powder, turmeric powder, and salt. Mix well and set aside.
Heat oil or ghee in a karahi, wok, or deep pan over medium heat. Add the chicken pieces and sear until browned on all sides, about 8-10 minutes. Remove and set aside.
In the same pan, add minced garlic and ginger, and cook 1 minute, or until fragrant.
Add the chopped tomatoes. Cook for 15 minutes, or until the tomatoes break down and form a thick sauce.
Return the chicken to the pan and add the reserved spice mix. Stir well to coat the chicken.
Add the slit green chilies. Simmer, uncovered, 20-25 minutes, stirring often, or until the chicken is cooked through and the oil begins to separate from the sauce. The sauce should thicken even more, coating the chicken pieces.
Garnish with chopped cilantro, julienned ginger, and lime or lemon wedges. Serve hot.