To a wok / kadhai kept over medium-heat, add 2 tablespoons oil.
Shallow-fry the cubed potatoes till they turn golden brown. Using a slotted spoon, transfer the potatoes aside on a plate.
Instant Pot Method
Add oil to the steel insert and press the Saute function. Press the Adjust button to move the selection to “low” and wait till the display reads “Hot.”
Add onions, along with ginger, garlic, green chilies and fry them till they turn soft.
Add salt, coriander, cumin, and chili powder along with tomatoes. Mix them well.
Add a cup of water and deglaze - scrap any bits stuck to the bottom of the inner pot.
Add spinach and mix it well. Place the trivet over the spinach mixture.
Transfer the potatoes to a steel bowl. Keep the steel bowl on the trivet.
Pressure cook on high for 4 minutes. Quickly release pressure when the cooking cycle is complete.
Remove the steel bowl and trivet.
Use an immersion blender to puree the spinach mixture to a fine paste. If using a blender wait for the contents to cool down for at least 10 minutes.
Set the saute function in the Instant Pot to low.
Add the potatoes along with garam masala and lime juice. Stir it in.
Let the potatoes simmer in the Instant Pot for 5 minutes.
Take it off the heat and serve hot with rotis or rice.
Notes
Stovetop Method
In a saucepan kept over medium heat, add a cup of water and once the water comes to a boil, add spinach and let it cook in it for 2 minutes or till the stems soften. Turn off the heat and set it aside. [I cook the spinach and don't blanch it. To blanch, read the notes section].
Meanwhile, heat oil in a wok or a kadhai kept over medium heat. Shallow fry the potatoes till they turn golden brown. Fry them in batches if needed. Using a slotted spoon, transfer the potatoes to a plate.
In the same wok, add onions, along with ginger, garlic, and green chilies, and fry them till they turn soft.
Add salt, coriander, cumin, chili powder, and tomatoes. Mix them well.
Add tomatoes and fry them till they are soft. Turn off the heat and let the mixture cool down for 5-10 minutes.
Transfer the onion-tomato mixture and the spinach along with water into a blender. Blend it into a smooth puree.
Add the pureed mixture to the wok and set it over medium heat. Add the potatoes and continue to cook till it is fork-tender.
Add garam masala and lime juice. Stir it in.
Take it off the heat and serve it hot with rotis or rice.
Notes (tips/variations)
The recipe below is a simple one for home cooks making weekday dinners. If you have some time on your hands, try these different variations that will help you tailor the recipe to your desired taste and texture.
To make it bright green - Blanching helps retain the green color in the spinach. Add spinach and a pinch of salt to boiling water to blanch. Cook for a couple of minutes or till the stem softens. Immediately transfer it to a bowl of cold water to stop cooking. Blanching causes nutrient loss, so I prefer to cook the spinach and use water to puree it.
Creamy vs. Coarse texture - you could puree the spinach till it is smooth and silky or just coarsely grind it so that you get some texture. Personally, I like the one with some texture, but the pureed version is definitely the most popular one.
Saag palak - Use spinach and mustard greens in a 1:1 ratio.