Step 1: Prepare the Poha Binder

In a strainer, rinse 1/3 cup of poha (rice flakes) with water. Drain all the water and let it rest for 5 minutes to soften. Afterwards, mash the poha thoroughly with your hands until it forms a dough-like consistency, similar to mashed potatoes. Set this aside to use as a binder.

Step 2: Sauté Vegetables and Spices

Heat 1 tsp of oil and 1 tbsp of butter in a pan over medium-high heat. Add 1/2 finely chopped medium-sized onion and 1 tbsp of finely chopped garlic. Sauté for 2-3 minutes until the onions are translucent. Add 1/3 cup each of finely chopped french beans, carrots, and boiled green peas, along with 1-2 finely chopped green chillies. Stir-fry on high flame for 2-3 minutes. Reduce the flame and add 1/2 tsp turmeric, 1 tsp red chilli powder, 2 tsp dry mango powder, 1 tsp cumin powder, and a pinch of garam masala. Mix well and cook for a few seconds.

Step 3: Make the Patty Mixture

Grate 5-6 medium-sized boiled potatoes directly into the pan with the cooked vegetables. Add salt to taste. Mix and mash everything together. Now, add the prepared mashed poha and 1 tbsp of chopped fresh coriander. Use a potato masher to combine all ingredients into a uniform mixture. Cook this mixture for another 3-4 minutes on high flame, stirring continuously.

Step 4: Cool and Shape the Patties

Transfer the hot patty mixture into a bowl and allow it to cool down completely to room temperature. Once cooled, cover the bowl with cling film and refrigerate for at least 15 minutes to let it firm up. After chilling, take a portion of the mixture, roll it into a ball, and then flatten it between your palms to form a round patty. Adjust the shape and size to be slightly smaller than your burger buns.

Step 5: Prepare the Coating

To make the slurry, combine 1 cup of refined flour, 1/2 cup of cornflour, and salt to taste in a bowl. Gradually add cold water while whisking continuously to create a smooth, semi-thick, lump-free batter. Stir in 1 tbsp of oil. In a separate shallow dish, place the panko bread crumbs and season them with a little salt and freshly ground black pepper.

Step 6: Coat the Patties

Take a shaped patty and dip it into the prepared slurry, ensuring it is evenly coated on all sides. Lift it out, allowing any excess batter to drip back into the bowl. Immediately transfer the coated patty to the seasoned panko bread crumbs. Gently press and cover the patty completely with the bread crumbs.

Step 7: Fry the Patties

Heat oil in a pan for deep-frying to a temperature of 170°C (moderately hot). Carefully slide the breaded patty into the hot oil. Fry on medium-high heat for a few minutes on each side until it turns golden brown and becomes crispy. Once done, remove the patty from the oil and place it on a strainer to drain any excess oil.

Step 8: Toast Buns and Assemble the Burger

Melt a small amount of butter on a hot pan. Place the burger buns, cut-side down, on the pan and toast until they are golden brown and slightly crisp. To assemble, take the toasted bottom bun, spread a generous layer of mayonnaise, top with shredded lettuce, and place the hot, crispy veggie patty. Cover with the top bun. Your homemade crispy veggie burger is ready to serve.

• Using soaked and mashed poha (rice flakes) as a binding agent provides a great texture without a floury taste.

• For a firmer patty without a binding agent, use less starchy potatoes like 'Pahari aloo' or 'Indori aloo' which have lower water content.

• Grate boiled potatoes instead of mashing them to avoid lumps and achieve a uniform consistency in the filling.

• Shape the patties to be slightly smaller than the burger buns, as they will increase in size after coating and frying.

• Ensure the coating batter is semi-thick; if it's too thick, the coating might remain raw inside, and if it's too thin, it won't hold the breadcrumbs.

• Fry the patties in moderately hot oil (around 170°C) to get a crispy exterior while ensuring the inside is heated through without absorbing excess oil.

• Add a slice of cheese on top of the hot patty for a cheeseburger.

• Use different sauces like peri-peri mayonnaise, tandoori mayonnaise, or schezwan sauce for a flavor twist.

• To freeze the patties for later use, substitute fresh onion and garlic with onion powder and garlic powder to extend their shelf life.