Heat a pan over medium flame. Pour oil and allow it to heat up.
Then pour the cream and onion paste into the pan. Give it a good stir.
Bring it to a boil while stirring continuously. Cook for 8-10 minutes or until the curd mixture thickens. The raw smell of the onion and garlic will also disappear.
Pour water and give it a good stir. Keep stirring until the curry is smooth and lump-free.
Add sugar and salt. Mix well. Allow it to simmer for a minute.
Add chopped potatoes. Mix well. Bring it to a boil.
Lower the flame. Cover it with a lid. Cook for 10-15 minutes or until the potatoes are fully cooked.
Uncover the pan and give it a stir. Check if the potatoes are cooked.
If it is fully cooked, then turn the flame off.
Otherwise pour a little water and cover it again. Cook for a few more minutes.
Add chopped spring onions (green part) and butter. Give it a good mix.
Pour the aloo ki sabji into the serving bowl.
Garnish with more spring onions. Serve hot!