First cook all vegetables, potatoes, cauliflower, capsicum, green peas (if you have frozen peas then no need to cook them, as they are already cooked) then add 1½ cup water in a pressure cooker and cook till 3 whistles
Drain all the water from cooked vegetables in a clean pot, and keep aside (don't throw that water, use it for preparing bhaji)
Now lightly smash the vegetables with the help of a smasher
Don't smash too much, don't make its paste.
Further heat 2 tablespoons of cooking oil and 2 tablespoons butter in a kadhai.
Now add 1 teaspoon shah jeera and bay leaf in it.
When jeera starts crackling then add onion paste to it, and cook until it turns light golden brown.
Now add ginger garlic paste to it, cook for 1 minute. then add red chilli powder, pav bhaji masala, turmeric powder, coriander powder, salt, and a pinch of food colour into it.
Mix it well for 4-5 minutes till oil oozes out on a medium flame.
Now add tomato puree to it.
Mix it well and cook for 2 minutes
Finally, add cooked vegetables to it.
Mix it well and add 1 cup of hot water ( which was kept aside after draining vegetables, in step 2)
In the end, add the remaining 2 tablespoons of butter and chopped coriander leaves. Now your bhaji is ready to serve.