Peel 6 medium size boiled potatoes and mash it. Then add 2 chopped green chili, 1/2 tsp red chili powder, 1 teaspoon salt and 1/2 teaspoon dry mango powder (amchur powder) in it. Mix it well.
Apply some oil or ghee on your palms and make medium size tikki by rolling the mashed potatoes with your palms then flatten it slightly.
Heat oil in a pan or tawa then gently place 2 to 3 aloo tikki over it and shallow fry. Flip it gently when one side turns golden brown. cook it at medium flame until both the sides turn golden brown.
Now, spread butter on two bread and toast it slightly in the same pan or in the other pan.Once the bread is toasted, smash and spread hot tikki over one side of bread then sprinkle chaat masala over the tikki. Add tamarind chutney, coriander chutney and thinly sliced onion over it.
Serve it hot and you can also serve one bread tikki sandwich in four bite size portion, which will be very easier to eat as well.