Step 1: Prepare the Pork: Trim any silver skin from the pork tenderloin. Slice it crosswise into 1-inch thick medallions. You should get about 4-6 pieces.
Step 2: Pound the Pork: Place each medallion between two pieces of plastic wrap or in a large zip-top bag. Using a meat mallet (the flat side) or a heavy-bottomed pan, pound each piece evenly until it's about 1/4-inch thick and significantly larger in diameter (roughly 6-8 inches across).
Step 3: Season the Pork: Season both sides of the pounded pork cutlets generously with salt and freshly ground black pepper.
Step 4: Set Up Breading Station: In a shallow dish, combine flour, paprika, garlic powder, onion powder, 1 tsp salt, and 1/2 tsp black pepper. Whisk well. In a second shallow dish, whisk eggs and milk. In a third shallow dish, place panko breadcrumbs.
Step 5: Bread the Pork: Dredge one pounded pork cutlet in the seasoned flour, shaking off excess. Dip into the egg wash, letting excess drip off. Transfer to panko breadcrumbs, pressing firmly onto both sides to ensure a thick, even coating. Repeat with remaining cutlets.
Step 6: Rest the Breading: Place breaded cutlets on a wire rack set over a baking sheet. Let them rest for 10-15 minutes to help the breading adhere.
Step 7: Heat Oil: In a large, heavy-bottomed skillet, pour enough oil to reach about 1/2-inch depth. Heat over medium-high heat to 350-360°F (175-182°C).
Step 8: Fry the Cutlets: Carefully place 1-2 breaded cutlets into the hot oil, without overcrowding. Fry for 3-4 minutes per side, or until deeply golden brown and cooked through (internal temperature 145°F/63°C).
Step 9: Drain and Keep Warm: Transfer fried cutlets to a wire rack set over paper towels to drain excess oil. Keep warm in a low oven (200°F/95°C) while frying remaining cutlets.
Step 10: Assemble Sandwiches: Lightly toast hamburger buns. Place a fried pork cutlet on the bottom bun. Top with dill pickle slices, sliced onion, and mustard. Add the top bun and serve immediately.