Add all the ingredients, except lemon juice and water, for the chutney into the small jar or a chutney jar of a mixer grinder. Add 1 tablespoon of water and blend into a light coarse chutney. Only if necessary, add the remaining water.
Stir in the lemon juice and mix. Set aside.
Heat oil in a kadai over medium heat. Add mustard seeds and curry leaves, and allow to splutter.
Add ginger garlic paste, green chillies, turmeric powder, red chilli powder and coriander powder. Saute for 1 minutes or until fragrant.
Add salt and mashed potatoes and mix to combine. Mash lightly, add a tablespoon of water if necessary.
Add green peas and mix to combine. Allow to cook for 2 minutes. Add chopped coriander leaves and combine. Set aside.
Using a spoon or butter knife, apply a spoonful of chutney on two slices of bread. On one slice, assemble the sandwich with a spoon of aloo masala, sliced tomato, cucumber, onion and capsicum. Sprinkle some sandwich masala and cover with the other slices.
Spread some butter on the outside part of both slices. Grill over a pan or use a sandwich maker and toast until golden brown on both sides, about 2-3 minutes.
Cut and smear with some more butter, chutney, ketchup and top it off with some sev. Serve hot!
Bread: You can use white bread or sandwich bread which is slightly thicker and larger in size.
Can I make this sandwich without a sandwich press? Yes, you can grill it on the stove. However, I recommend using a sandwich press as it helps hold the masala better, making it neat to serve and eat.
Can this be made without onion and garlic? Yes, you can omit the garlic in the masala and can add extra chopped capsicum for a nice crunch instead of using raw onions.
Can I add cheese? You can top the sandwich however you’d like! Grated cheese would work well both as a filling and a topping.
Can I make this without butter? Butter helps the bread to brown and crisp up well while grilling and this helps to hold the sandwich together - which is important for this recipe as we have a thick filling. If you would like to reduce the butter, you can skip adding it as a topping afterwards.