Pat the White Fish Fillets dry and cut into 2–3 cm thick pieces if large; set aside so they’re ready to absorb the marinade.
In a bowl mix Lemon Juice, Salt, Turmeric Powder, Ginger-Garlic Paste, Kashmiri Red Chili Powder, Hot Red Chili Powder, Garam Masala, Cumin Powder and Mustard Oil to make a spicy, tangy paste; rub this all over the fish pieces and marinate for 20–30 minutes in the fridge.
Meanwhile prepare the batter: whisk together Besan (Gram Flour), Rice Flour, Ajwain (Carom Seeds) and a pinch of Baking Soda in a bowl, then season with a little salt and extra Kashmiri chili if you like.
Slowly add cold water and finally Club Soda to the dry mix to make a thick, smooth batter that coats the back of a spoon — it should be thicker than pancake batter but fluid enough to cling to the fish.
Heat a deep, heavy skillet or kadai with enough oil (use mustard oil for authentic flavor) over medium-high until hot; test by dropping a little batter in — it should sizzle and rise slowly.
Working in batches, dip each marinated fish piece into the batter to fully coat, then carefully slide into the hot oil and fry until deep golden and crisp on all sides, about 3–5 minutes per batch depending on thickness. Don’t overcrowd the pan.
Use a slotted spoon to transfer the fried fish to paper towels to drain excess oil and keep them warm while you finish the remaining batches.
Serve the Fish Amritsari hot with a bowl of Mint Chutney, sliced Red Onion tossed with a pinch of Chaat Masala, lemon wedges from Lemon, and a scatter of chopped Coriander Leaves. Enjoy immediately for the crispiest texture.
