Heat oil in a heavy-bottomed pan or wok, add the onions and saute, until golden.
Add the ginger-garlic paste, green chillies, and saute for a minute.
After the ginger-garlic is sautéed, add tomatoes, and cook over high heat.
Once the tomatoes begin to darken, add in the cauliflower, peas, bell peppers, along with ½ cup water and salt. Cover and cook until the veggies are soft.
Now throw in the boiled potatoes along with the pav bhaji masala and chili powder.
Later add 1 ½ cup water to make a thick, gravy-like consistency.
Using a masher, mash down the veggies until most of them are broken down.
After the bhaji comes to a boil, turn up the heat, and cook the veggies over high heat for five minutes, stirring constantly.
Garnish with freshly chopped onions, coriander, lemon juice, and a dollop of butter.
Serve it hot with pav and a tall glass of buttermilk.