Secure the lid of cooker and cook under full pressure for 25 minutes. Lower the heat and simmer for another 10 minutes. Allow the pressure cooker to decompress before safely removing the lid. Allow to cool then mash until smooth. Set aside.
Heat a large frying pan or skillet over a medium heat and add the chopped bell peppers. Add half the water and cook until the peppers soften. Add the chopped tomatoes and cook for 2 minutes. Add the cooked and chopped potatoes, mashing them into the pan using a potato masher.
Add 75g of the cooked green peas, 1.5 teaspoons of the chilli powder and 1.5 tablespoons of the garlic paste. Add 60g of the butter and continue to mix and stir, ensuring the vegetables do not stick to the pan. Mash the vegetables, adding the remaining water, and mix well. Add another 60g of the butter, followed by 1.5 tablespoons of the Mumbai bhaji masala, salt and 20g of the finely chopped coriander.
Continue to mix and mash until the mixture has thickened and the oil has separated.
Use a spatula to push the pav bhaji to the sides of the pan and add the remaining butter to the centre of the pan. Add the onions to the melted butter, the remaining ½ tablespoon of garlic paste, 1 teaspoon of chilli powder, 1 tablespoon of Mumbai bhaji masala and the remaining chopped coriander.
Mix well and cook for 3-5 minutes. Add the lime juice. Fold the cooked vegetables from the sides of the pan into the onion mixture and continue to cook and mash the bhaji to a purée. Add another 60ml of water if needed. Set aside and keep warm.
For the toasted bread rolls, heat the butter in a large frying pan or skillet and add the coriander, chilli powder, and Mumbai bhaji masala.
Spread the mixture out in the pan and once the butter has completely melted, spread all 8 halves of the sliced buns onto the pan, covering the mixture, toasting lightly on both sides for 10-15 seconds, absorbing the flavours.
To serve, divide the bhaji between 4 bowls or plates and top with chopped coriander. Add the onions, toasted bread rolls, lime wedges for squeezing and a teaspoon of butter to each serving.
Note: If you'renot using a pressure cooker, place the rinsed peas in a deep saucepan and cover with 1.9l of hot water. Leave to soak for 2 hours. Bring the peas and soaking water to the boil, then partially cover with a lid and cook over a medium heat for 1.5 hours until the peas are mushy. Leftover green peas can be stored in a zip-top bag in the freezer for 3 months. Thaw before using.