In a medium bowl, combine mustard, honey, lemon juice, salt, cayenne and red pepper flakes. Reserve 1/4 cup marinade in a separate dish if making a salad.
Slice chicken in half to create two thin filets. Cut filets into 6-8 strips each. Repeat with remaining chicken breasts. Add chicken strips to marinade. Toss to coat well. Cover and chill for at least one hour.
Preheat oven to 425°F. Prepare a baking sheet with parchment paper.
Mix panko and plain breadcrumbs in a small bowl. Taking one chicken strip at a time, toss in breadcrumbs. Transfer to parchment lined baking sheet.
Bake for 25-30 minutes or until desired crispness is reached. After the first 10 minutes, flip chicken strips. Serve with your favorite dipping sauce or on top of a salad.