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. Remove tough tendons. (See note.)
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, depending on your oven, watching very carefully to prevent burning, until just about browned to your liking.
Pour browned panko 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. There's no need to flip them.
Serve right away with ketchup or dipping sauce of your choice (if you like — the chicken is nice and flavorful on its own).