Preheat oven to 425F. Pour melted butter in the bottom of a large baking sheet and set aside.
In a shallow bowl, combine 1 teaspoon salt, 1/2 teaspoon pepper, and flour. Dredge chicken in flour mixture, shaking off excess.
In a resealable plastic bag, combine toasted breadcrumbs, remaining 1 teaspoon salt and 1/2 teaspoon pepper, paprika, and Parmesan. Whisk egg whites and 2 tablespoons water in a shallow bowl. Dip chicken pieces in egg white mixture, a few at a time, then transfer to breadcrumb bag, seal and shake until nuggets are coated. Repeat with remaining chicken and place chicken nuggets in a single layer on prepared baking sheet.
Bake chicken nuggets at 425F 18-20 minutes, flipping nuggets once halfway through baking, until chicken is a deep golden brown.
Make the honey mustard dip: In a small bowl, whisk all dip ingredients until smooth. Serve with hot chicken nuggets. Enjoy!