Add 2 tablespoon of oil in a pan/ tava.
When the oil starts to smoke add cumin seeds in it. Then add mustard seeds and half a cup of onion in it.
Saute the onion until they are light pink and then add ginger-garlic paste in it. The ginger-garlic paste is optional so add only if you feel like.
Saute all the ingredients for another minute and then add finely chopped capsicum and mushrooms in it.
Mix everything and add spices now. Start by adding 2 tablespoons of pav bhaji masala and salt.
Mix the spices and cook for 3-4 minutes until the veggies become little soft.
Then add 3 medium sized finely chopped tomatoes( approx 1 cup) and chopped green chilies in the tava.
Now, add chopped coriander leaves with the tomatoes and cook for 5-6 minutes on medium heat till the tomatoes become soft and pulpy.
When the tomatoes are soft and pulpy pour 3-4 tablespoon of water and mix everything.
Now, mash the veggies with the back of your ladle while cooking the masala. Cook and mix the masala for 2 minutes.
Now, when the masalas are about to cook, take tomato masher and mash and mix the masala for 2-3 minutes.
Your masala is ready now slide it one side and take pav buns, cut them from between. Add a teaspoon of butter and put buns on it.
Switch off the heat and sandwich the masala in the pav and take them out in a plate.
Sprinkle some coriander leaves and serve with sev and masala tea.