Heat oil in a pan over medium-high heat. Once the oil is hot, add cumin seeds and let them crackle for 4-5 seconds.
Toss in the chopped green chilies and grated ginger and cook for 20 seconds.
Add turmeric powder, Kashmiri red chili powder, and the mashed potatoes. Mix well.
Sprinkle salt, garam masala, amchur, and chopped cilantro. Stir for one minute. Turn off the heat and let the filling cool.
The filling should be dry, not pasty. Wet filling will leak into the batter. If your potatoes feel sticky, cook the mixture a little longer to dry it out.
Prepare The Batter
In a mixing bowl, whisk together besan, rice flour, carom seeds, turmeric, hing, baking soda, lime juice, green chilies, cilantro, and salt.
Slowly pour in water while whisking. Aim for a lump-free batter that coats the back of a spoon but still drips off. Think pancake batter, not paste. Let the batter rest for 5 minutes. This step makes the coating crispier.
Stuff The Bread
Trim the crusts off the bread slices if you like (optional, but classic).
Spread 2 to 3 tablespoons of the potato filling on one slice. Press lightly. Top with a second slice. Press the edges to seal. Cut diagonally into two triangles. Repeat for all slices. You should have 8 stuffed triangles.
Heat The Oil
Pour oil into a deep pan or kadai. You want enough oil so the pakoras float freely without touching the bottom, about 2 inches deep. Heat over medium flame. To test the temperature, drop a tiny bit of batter into the oil. It should rise to the surface within 3 to 4 seconds without browning instantly. That is the sweet spot.
Dip And Fry
Hold a stuffed triangle by one corner. Dip it fully into the batter. Let the excess drip off for a second.
Slide it gently into the hot oil. Fry 2 to 3 pieces at a time. Do not overcrowd the pan.
Fry on medium heat for 3 to 4 minutes per side, turning once, until deep golden brown and crisp. Lift with a slotted spoon. Drain on a wire rack or paper towels. Serve hot.