Cook cauliflower , peas ,carrots , green pepper together in a pressure cooker and keep it aside.
Soak Kashmiri Red Chilli & Garlic in 1/2 Cup of Hot Water for 15- 30 minutes. Grind them into a fine paste and set it aside.
Heat 2 tbsp butter in a pan, add onions and saute until it turns light brown. Add a pinch of salt while frying onions. It will help to evaporate the water & fry quickly.
Add red chilli - garlic paste & ginger, green chillies and saute for 30-40 seconds.
Add the diced tomatoes to it and cook on medium heat for three to four minutes, stirring continuously or till oil separates from the masala.
Add turmeric powder, red chilli powder , 1 tsp pav bhajji powder to the mixture.
Now add the cooked vegetables & mashed potatoes to this mixture along with 1-1.5 glasses of water.Using a potato smasher , press the vegetables a few times till all of them are completely smashed.Bring it to a boil and simmer for ten minutes. Add the rest of the pav bhaji masala and salt now.
Cook on medium heat for 2-3 minutes and stir continously.
Garnish the Pav bhaji with chopped onions and lemon juice.
For Serving :
Heat some butter in a tawa. Slice pav horizontally into two and pan fry in butter for half a minute, pressing two or three times or till pav is crisp and light brown.
Garnish the Pav Bhaji with chopped coriander leaves, a little of butter and serve hot with pav accompanied with remaining chopped onion and lemon wedges.