Peel and wash the sweet potatoes and carrots. Chop into big chunks. Roughly peel the drumsticks and cut into 4” long pieces.
Heat vegetable oil in a large pot set over medium-high heat. Sauté the onions till they begin to turn golden brown. Add ginger and sauté for another 1-2 minutes. Add ground tomatoes and minced garlic, and cook covered for 10 mins over medium-high heat till the tomatoes don't taste raw.
Next add salt, turmeric, coriander powder, chili powder and cook for another 5 mins, stirring intermittently.
Add the stock, sweet potatoes and carrots. Cover and cook over a low medium flame for 20 mins or till the vegetables are partially cooked. Add more water if required. Add the drumsticks, peanuts, tomato puree and cook for another 15 minutes on low medium heat.
While the stew is simmering, heat oil in a pan. To this add 1 tablespoon of garlic-chilly paste and the chicken pieces. Brown the chicken over a high flame for about 4-5 mins. Turn them using tongs so that both sides are evenly browned. When done, empty the contents and keep aside.
Pour some water into this pan and add to the stew to extract the flavor from the cooked chicken.
Now add peanut butter, tamarind water and the chicken pieces. Cook till the pieces are done. Cooking time of the chicken will depend on the size of the pieces.
If you don't want the chicken pieces very large, cut them into small pieces after they are cooked and toss back into the stew.
Adjust the seasoning before serving. Add chopped onions and squeeze some lemon juice over it. Serve with rice or pao.