Pav Bhaji is most famous for being Mumbai Street Food. To bring it into the house and cook it at home, is to take your home to a side stall in India.
I actually found this recipe watching a YouTube video, where an interviewer goes to a roadside stall and watches one of the most famous stalls that sits on Juhu beach. And I watched what the guy did - over and over and over - to make his Pav Bhaji look SO decadent and comforting - even through a camera.
In a heated pan, you add your bell pepper, tomatoes, and onion. Smash potatoes in - and this is where the spice and butter magic starts!
Create a little (a lot) of room in the middle of the dish (this is why you need a big pan!). Add the butter and let it melt slowly, then add the ginger-garlic paste and spices in. Continue to mix and mash.
Basically, for the next 20 or so minutes, you are repeating adding spices (moderately), adding some water - and mashing. You need to make sure the vegetables can't be distinguished from one another and they are one big masala family - that's when you know your pav bhaji is ready to go!