Preheat oven to 425°F (220°C). Set a wire rack over a sheet pan (line with parchment if you want easier cleanup).
Spread panko on the sheet pan, spray lightly with oil, and bake 4–6 minutes, stirring once, until golden. Transfer toasted panko to a shallow plate.
In a bowl, whisk egg, mayonnaise, Dijon mustard, flour, salt, and black pepper until smooth.
Add chicken tenderloins and toss until fully coated.
Press each tender into toasted panko until evenly coated.
Place tenders on the wire rack in a single layer and spray tops lightly with oil.
Bake 14–18 minutes, until golden and chicken reaches 165°F in the thickest part. Optional: broil 1–2 minutes for extra browning (watch closely).
Rest 2 minutes and serve warm with your favorite dip.
