Melt ghee in a saucepan on medium heat, and add onions.
Once the onions begin to brown, add ginger, garlic, and serrano pepper. Stir-fry for a minute then add tomatoes. Mix well and cover pan for five minutes.
Add the spices and stir-fry for a minute before adding the ground lamb.
Once the lamb is fully brown, add peas, carrots, potatoes and tomato sauce. Combine well, raise heat and bring to a boil.
Once boiling, put on cover and cook for another few minutes. Then remove from heat and place inside the Wonderbag. Cover the Wonderbag with the insulating lid and pull drawstring to secure.
After 4-5 hours, serve.