Warm up ghee on low medium in a cooking pot/kadai. Temper the ghee with whole spices. Fry for 5-7 seconds taking care not to burn.
Add hing, cilantro stems, ginger and green chillies next. Again fry for 5-7 seconds to perfume the ghee.
Next add all the spice powders (except amchur & garam masala). Add ¼ cup water so that the spice powders don't burn. Fry the spices hwile stirring for 15-20 seconds on low medium heat or so untill you smell a nice aroma.
Add the crushed tomatoes now. Cook the tomatoes for 2-4 minutes or until you see ghee starting to separate on the sides of the pot. Don't dry out the tomatoes too much.
Add in the boiled potatoes, sprinkle salt. Mix well and cook the potatoes for 2-4 minutes with tomato and spices. Avoid stirring too much else the potatoes will start breaking. Don't skip this step, it gives chance to potato to absorb the flavors of spices.
Pour 1.5 cup hot water to begin with, mix well and let the curry come to a boil.
Once boiling, reduce heat to low, cover and let simmer for 10-12 minutes on low heat. Halfway, check for water and adjust if as per desired consistency. You can mash a few big pieces of potatoes using back of the spoon at this time, this helps in thickening the curry. Make the curry as thin or thick as you like.
Switch off the stove, taste and adjust the salt if needed and mix in the amchur powder, kasuri methi and garam masala powder. I also add in a teaspoon of ghee for finishing. Combine and let the aloo sabzi rest while you make pooris.
Reheat if needed and garnish with chopped cilantro before serving.