In a large bowl, season goat meat with onions, tomato, ginger, garlic, curry powder, salt, and pepper. Mix well and marinate in the refrigerator, overnight.
Preheat the oven to 375 degrees F.
Remove meat from marinade. In a large braising pot, over a moderately high heat, brown off meat in 2 tablespoons ghee or oil until golden brown on all sides. When done browning all of the meat, pour excess fat from pot. Add the rest of ghee or oil to pot and all of the reserved marinade and some hot sauce and saute for 6 minutes. Then, return meat to pot with enough water to just cover the meat and bring to a boil. Cover and put pot in the oven for 1 1/2 hours. Add the potatoes to the pot, return the pot to the oven and cook for anther 1/2 hour, or until meat is tender.
Remove the meat from the pot, place on a platter and cover with aluminum foil. Return the pan to the stove over medium heat and cook until sauce is thickened. Season with salt and additional hot sauce, if desired. Garnish meat with scallions.