Dry roast the spices mentioned, cool and grind to a fine powder. Store in an airtight jar.
Wash and boil the potatoes with skin till they are fork tender. Let cool then peel.
Pound the onion and ginger and chilli if using in a mortar and pestle till they are mixed together. This will help in releasing flavours even better.
In a kadhai, heat 1 tbsp ghee. Fry the potatoes in small batches till they wrinkle and semi crisp on the outside. Prick with a fork and keep aside.
Add more ghee if need be. Add the jeera. Let it pop, but not burn.
Add the dry red chilli. Let it fry well to flavour the oil, then take it out and keep aside.
Add the onion, ginger and mix. Fry till it begins to brown and soften.
Add a pinch of salt, chilli and a tsp of the roasted masala and mix to combine well.
Add the potatoes and stir well to coat it with the spice mix.
In a bowl take the mango pulp and dilute it with some water. This is to prevent the pulp from getting burned or thicken too much while being cooked. Add this to the kadhai and stir well.
Add the amchoor powder, and season with salt according to taste.
Let the gravy thicken and cook well.
Just before turning off the flame, add another spoon of the roasted masala and the fried chilli and stir it in.
Take it out in your serving dish, sprinkle some more masala on top and serve with parathas, kulchas or plain steamed rice.