Add the oil to a wide and heavy iron kadai and let heat up till its a bit smoky.
Temper the oil with hing and cumin seeds and let crackle. Add the ginger and saute for 30 seconds.
Add the sliced onions and on low medium heat cook the onion till they are browned.
Add the peas and potatoes together, mix and saute with the onions for about 3-4 minutes stirring regularly.
Sprinkle the spice powders (except amchoor & garam masala) and add salt. Mix well and cover the wok and let peas and potatoes cook on low heat for about 6-8 minutes. Open and stir halfway once to make sure nothing is sticking to the bottom of the kadai, if so add a light splash of water, cover and let cook again until the poatoes and peas are soft.
Uncover and add the amchoor and garam masala and on high heat, saute the sabzi for about 3 minutes stirring regularly. You will see that the peas are shiny and the potatoes are falling apart, that makes this sabzi super delicious.
Garnish with chopped cilantro and serve warm. If you are planning to serve later, make sure that you transfer the sabzi to another dish and store.