You’ll need a rimmed baking sheet and a wire rack that fits inside.
Preheat oven to 425°F with a rack in the center.
In a large mixing bowl, stir together mayo, garlic, lemon juice, mustard, salt, some pepper and two tablespoons of the parmesan. Dry chicken well with paper towels. Add chicken and stir to coat well. Set aside.
On a rimmed baking sheet, mix together the panko, remaining two tablespoons parmesan and the butter with your hands. Spread out in a single layer and bake for about 4 minutes, watching very carefully to prevent burning, until just about browned to your liking. (They won’t brown much more once on the chicken.) Pour onto a large plate or into a wide, shallow bowl. Place wire rack onto baking sheet.
Use tongs to remove each chicken tender from the bowl and dredge in panko until well coated, then lay on wire rack with a little bit of space between tenders.
Bake for about 15 minutes, until chicken is just cooked through. Serve right away with ketchup or dipping sauce of your choice (if you like — the chicken is nice and flavorful on its own).