In a mixie or blender, take coriander leaves, chaat masala powder and green chilies.
Just add a pinch or two of salt as chaat masala already has salt in it.
Grind the chutney ingredients till smooth. No need to add water. But if you cannot grind, then add 1 or 2 teaspoons of water.
Collect the coriander chutney in a bowl.
Check the taste and add more salt if required.
Cover and keep the chutney aside if you are making veg sandwiches immediately or else refrigerate.
Boil or steam the beetroot and potatoes till they are tender. You can steam both the veggies in a pan, stove-top pressure cooker or in the instant pot.
When cooled, peel both the vegetables. Then thinly slice the beetroot and slice the potatoes as well.
Peel and thinly slice onion and cucumber.
Thinly slice the tomatoes as well. Peel and rinse the onions. Thinly slice the onions.
Making veg sandwich
Trim the edges of the bread slices if you want.
Butter the bread slices evenly and very well.
Now apply the coriander chutney to the slices.
Place all the veggie slices one by one.
Sprinkle the black salt and chaat masala on each one of them or alternately.
Cover the sandwich with the bread slices with the butter and chutney on them.
Slice into triangles or rectangles.
Serve Bombay veg sandwich immediately with tomato ketchup and the coriander chutney. Do not let them rest as they become soggy.
You can cook the potato in the microwave. Wash the potato well. Prick the potatoes with a fork and microwave in the oven for 4 to 5 minutes.
When the beetroot and potatoes are getting cooked, you can slice the other vegetables and make the chutney.
You can use whole wheat bread or brown bread or multigrain bread or white bread. But the best taste in veg sandwich comes with white bread and this is how it is made by the street food vendors in Mumbai.
Dairy butter is used in these veg sandwiches. But you could easily use vegan butter.
You can also toast these veg sandwiches if you prefer.