Preheat your oven to 200 °C (390 °F) (or 180 °C fan‑forced if your oven uses that setting).

Toast the panko: Spread the panko on a baking tray, spray lightly with oil (spray vertically so you don’t blow the crumbs off the tray). Bake for ~3‑5 minutes until the panko is light golden. Transfer to a bowl. Toasting the panko beforehand helps prevent it from soaking up too much moisture, resulting in a crispier coating.

Place a rack on a baking tray (optional but helps baking more evenly).

Prepare the batter: In a bowl whisk together the egg, mayonnaise, Dijon mustard, flour, salt and pepper until combined. Add the chicken tenderloins into that batter and toss to coat.

Crumb the chicken: Using tongs pick up each piece of battered chicken, place into the toasted panko bowl, sprinkle extra breadcrumbs over if needed, press down gently so the crumbs adhere well. Transfer onto the prepared baking tray.

Lightly spray the crumb‑coated chicken with oil, and optionally sprinkle a small amount of salt.

Bake in the preheated oven for about 15 minutes (for medium sized tenders) or up to 20 minutes if the pieces are large. Avoid baking much longer to prevent drying out.

Once done, remove from oven and serve immediately—make sure to enjoy while warm and crunchy. Optionally sprinkle fresh parsley and serve with your choice of sauce (honey mustard, ranch, etc.).