Pat the walleye fillets very dry with paper towels. Check for pin bones and remove any with clean tweezers.

In a shallow bowl, combine cornmeal, flour, salt, paprika, garlic powder, onion powder, black pepper, and cayenne if using.

In a second shallow bowl, whisk the eggs with milk until smooth.

Dip each walleye fillet into the egg mixture, letting excess drip away, then press both sides into the seasoned cornmeal mixture. Shake off loose coating and place on a plate for 5 minutes so the crust can adhere.

Heat the oil in a large skillet over medium to medium-high heat until shimmering. Add the butter and let it melt without browning.

Add the coated fillets in a single layer without crowding the pan. Cook for 3–4 minutes on the first side until deeply golden and crisp.

Turn carefully with a fish spatula and cook for another 2–4 minutes, depending on thickness, until the second side is golden and the fish flakes easily and reaches 145°F (63°C) in the thickest part.

Transfer the walleye to a wire rack or paper towel-lined plate. Rest for 2 minutes, then serve hot with lemon wedges and parsley.