Set the Instant Pot to 'Saute' mode. Add the ghee or butter and the chopped onions.
Saute for 2-3 minutes, until the onions turn translucent.
Add the ginger-garlic paste and saute for a minute more. Hit 'Cancel' and turn off the Instant Pot.
Important: If there is any residue from sauteeing the ginger-garlic paste or onions, then add a little water and deglaze the bottom of the Instant Pot. And residue will trigger the 'Burn' notice for newer models of the Instant Pot.
Now add all the veggies, followed by all the spice powders - pav bhaji masala, coriander powder, Kashmiri red chili powder.
Add the canned tomatoes and ¾ cup of water. Mix well.
Close the lid of the Instant Pot and set it to Pressure Cook mode for 7 minutes.
Once the cooking cycle is complete, let the pressure valve come down on its own. Open the lid, and using a potato masher, mash all the cooked vegetables well. Add salt, lemon juice to season, a little butter and mix well.
To serve the pav bhaji, heat butter in a saucepan. Slit the dinner rolls or pav bread and toast them in the saucepan until the sides are golden brown. Serve the toasted bread, with chopped up red onions, a few wedges of lemon. Serve the bhaji garnished with chopped coriander leaves and more butter.
To make pav bhaji that tastes authentic, don't skip the butter. Ghee is a good substitute. For a vegan option, use vegan butter.
Use Kashmiri Chili Powder – it imparts a deep red color to any dish but gives the dish very little heat. A close substitute is paprika powder - although paprika is sweeter in taste.
While pressure cooking the veggies in the Instant Pot, add just enough water as specified in the recipe. Too much water will make this a stew. You want the bhaji to be the consistency of a mash, not a stew.
To balance out all that richness, use lemon juice to finish the dish. Mix it in with the mashed veggies before serving.