1. Toast spices in a dry skillet over medium-low heat for 3 to 5 minutes, stirring occasionally, until mustard seeds begin to pop. Cool completely and then grind into a powder.
2. In a large bowl, mix the beef, yogurt, lemon juice, ginger and garlic pastes, and spice mix. Marinate for 2 to 3 hours, or overnight for best results.
3. Heat oil in a large skillet or Dutch oven over medium heat. Add onion slices and fry until golden brown. Add the marinated beef and water; mix well and cover. Cook on a stove on low heat for 2 to 3 hours until the meat is completely tender and juices have soaked into the meat.
4. Stir fry the meat on medium heat for 2 to 3 minutes ( This is a very important part of our cooking process to bring out the flavors)
5. Garnish with onion, green chili, cilantro, ginger and lemon.
Serve hot with naan.