Trim fat from chicken breasts. Slice each breast into 3–4 even strips (about 1 to 1 1/2 inches wide) so strips are similar size for even cooking. If using chicken tenderloins, leave whole or halve lengthwise if very thick.

Marinate

Place chicken strips in a medium bowl. Add buttermilk, 1 tsp salt, 1 tsp black pepper, 1 tsp garlic powder, and 1 tsp paprika. Stir to coat, cover, and refrigerate for at least 30 minutes and up to 8 hours. The buttermilk tenderizes and seasons the chicken.

For the breading

Make dry mixtures

In a shallow wide bowl or rimmed plate combine flour and cornstarch. In a second shallow bowl mix panko, 1 tsp salt, 1/2 tsp black pepper, 1/2 tsp onion powder, 1/2 tsp smoked paprika and optional 1/4 tsp cayenne. The cornstarch in the flour mix helps crisp the crust.

Make egg wash

In a third bowl whisk together 2 large eggs and 2 tablespoons water until smooth.

Breading station

Set up the three bowls (flour mix, egg wash, panko mix) in a row so you can dredge efficiently: flour -> egg -> panko.

For dredging and frying

Dredge chicken

Remove one strip of chicken from the buttermilk, letting excess drip back into the bowl. Dredge evenly in the flour/cornstarch mixture, shaking off excess. Dip into the egg wash, then press into the panko mixture until well coated. Place on a wire rack set over a baking sheet. Repeat with remaining strips. For an extra-crisp double-coated finish, you can repeat the egg and panko step once more.

Heat oil

Pour 2 cups vegetable oil into a large skillet (cast iron or heavy-bottomed) to a depth of about 1/2 inch. Heat over medium-high heat until oil reaches 350°F (175°C) or a small piece of bread sizzles and browns in about 45–60 seconds. Maintain 325–350°F for frying.

Fry

Working in batches (do not crowd), carefully add breaded tenders to the hot oil. Fry for about 3–4 minutes per side, turning once, until golden brown and internal temperature reaches 165°F (74°C). Adjust heat as needed so the coating browns without burning before the chicken cooks through. Use a slotted spatula or tongs to transfer cooked tenders to a wire rack set over paper towels to drain excess oil.

Finish and keep warm

If frying in batches, keep finished tenders warm in a 200°F (95°C) oven on a baking sheet while you finish the rest. Sprinkle with chopped parsley and squeeze lemon if using.

To finish (optional)

Serve the chicken tenders hot with lemon wedges and your choice of dipping sauces (ranch, honey mustard, barbecue). Adjust salt to taste and garnish with parsley.