Crispy Chicken Fingers

1 large egg yolk
3 Tbsp. plus 1/4 cup mayonnaise
1 Tbsp. plus 1/4 cup Dijon mustard
1 1/2 tsp. Diamond Crystal or 3/4 tsp. Morton kosher salt, plus more
Freshly ground black pepper
1 1/2 lb. skinless, boneless chicken breasts (about 2 large)
1/2 cup extra-virgin olive oil
2 cups panko (Japanese breadcrumbs)
1 Tbsp. honey
3 Tbsp. finely chopped chives
Pinch of cayenne pepper

Place a rack in middle of oven; preheat to 450°F. Whisk egg yolk, 3 Tbsp. mayonnaise, 1 Tbsp. mustard, 1 1/2 tsp. Diamond Crystal or 3/4 tsp. Morton salt, and several cranks of black pepper in a large bowl until smooth.
Pat chicken dry with paper towels.
With your knife parallel to the cutting board, slice breast into 1/2"-thick cutlets Place in bowl and turn with tongs to evenly coat.
Set aside.
Heat oil in a medium skillet over medium. Add a pinch of panko.
If tiny bubbles appear instantly, you’re good to go.
Add remaining panko and cook, stirring, until golden brown, about 5 minutes.
Let panko cool in pan about 5 minutes.
Set chicken next to panko and place a wire rack set inside a rimmed baking sheet nearby.
Using tongs, place a piece of chicken in panko and pat all over with panko, pressing firmly to adhere.
Lightly shake off excess and place chicken on rack.
Repeat with remaining chicken, spacing evenly apart on rack.
Discard any remaining panko.
Bake chicken until cooked through and breadcrumbs are deep golden brown, 10–15 minutes.
Let cool slightly.
Stir honey, cayenne, and remaining 1/4 cup mayonnaise and 1/4 cup mustard in a small bowl; season with black pepper.
Add chives to sauce.
Serve chicken with sauce alongside for dipping.