Sheet Pan Honey Mustard–Pretzel Chicken

Preheat oven to 425°. Generously grease two rimmed baking sheets with cooking spray. In a large resealable plastic bag, crush pretzels with the back of a wooden spoon or rolling pin, until mixture is coarsely ground. Transfer to a shallow bowl.  In another shallow bowl, whisk together honey mustard and egg. In a medium bowl, season chicken with salt and pepper and toss to coat evenly with flour.  Dip each chicken piece in honey mustard mixture, letting excess drip off, then roll in pretzels, pressing in the pretzels with your fingers. Transfer to prepared baking sheets in an even single layer and spray generously with cooking spray.  Bake, turning halfway through, until chicken is cooked through and pretzels are golden, 12 to 15 minutes. Serve chicken with more honey mustard.