Mash potatoes and put into a bowl. Add red chilli powder, black pepper powder, garam masala powder, cumin powder, coriander powder and salt and mix well.
Scoop out the flesh from 4 tomatoes and reserve the pulp. Stuff the tomatoes with the potato mixture.
Heat 4 tbsps ghee in an iron kadai and place the stuffed tomatoes, open end facing down. Cover and cook on low heat, turning sides every 5 minutes till soft.
Mash with the back of a spoon till tomatoes and potatoes get properly mixed.
Grind the remaining tomato with the scoop out flesh from the 4 tomatoes to make a puree.Heat remaining ghee in a non stick pan, add the puree, sugar, salt and tomato ketchup and cook for 2-3 minutes, ensuring that it does not get too thick.
To serve put the tomato-potato mixture in serving bowls, pour the tomato puree over it. garnish with ginger, coriander leaves and crushed namakpara.