Said to have originated as a cheap fast food for the mill workers of Mumbai in the mid-nineteenth century, this simply translates as ‘bread’ (pav , a soft white roll) and ‘mashed vegetables’ (bhaji ). However, the generous quantity of butter, along with the exquisite spice blend, elevates this dish beyond the humble. The spice blend makes double the quantity needed for the recipe; store it in an airtight container for 3–4 weeks and use in place of garam masala.
Make the spice blend by placing all the ingredients except the amchur powder in a dry frying pan. Set over a medium heat and toast for a minute or two, until a deep, toasty aroma rises from the pan. Tip into a spice mill or pestle and mortar and grind to a powder, then transfer to a bowl and stir through the amchur powder while the spices are still warm. Set aside.
Add the potato and squash cubes to a saucepan and cover generously with boiling water. Set over a high heat, bring back to the boil and cook until tender, around 15 minutes. Drain well and set aside.
Place the cumin seeds in a saucepan and set over a medium heat to toast for a minute. Once you can smell their aroma wafting up from the pan, add the butter and allow it to sizzle and melt before tipping in the chopped red onion and stirring regularly for 10 minutes. Stir through the chilli, ginger and garlic and fry for a further 5 minutes before adding the tomatoes and 3 tablespoons pav masala spice mix. Fry for another 5 minutes until thick and fragrant, then add the cooked potato and squash along with 350ml water. Simmer steadily for 20 minutes until thick and rich, mashing with a potato masher as it cooks. Season to taste with salt.
Heat a large frying pan until hot and toast the rolls, butter side down, until crisp. Spoon the bhaji into bowls, scatter over the red onion slices and coriander and serve with a wedge of lemon to squeeze over and a roll to dunk in and scoop it up.