1. Preheat the oven to 400° F. Lightly grease with oil a large, non-stick baking sheet or roasting pan. If you don't have a non-stick pan line a regular pan with parchment and lightly grease with oil.
2. In a large skillet over medium heat toast the panko crumbs until lightly golden, stirring constantly. Remove from the pan and allow to cool.
3. In a food processor pulse the pretzels until coarsely ground (small crumbs with some small pretzel pieces) then add them to a medium bowl and mix with the panko crumbs. Wipe the crumbs out of the food processor.
4. Add the oil, mustard, honey, water and vinegar to the food processor and pulse until smooth.
5. Season with salt and pepper. Taste and adjust the flavor to suit your own tastes by adding more mustard or honey.
6. Pound the chicken breasts out to an even thickness using a mallet. Season well with salt and pepper.
Set up a dredging station:
7. Pour half of the dressing into a large shallow bowl or dish, put the flour on large plate and add half the pretzel mixture to a large, shallow bowl or dish.
8. Working one at a time and using tongs dredge the chicken in the flour then into the dressing allowing excess to drip off then into the pretzel crumbs patting them on if needed. Place on greased baking sheet. Add the remaining half pretzel crumbs to the dish as needed.
9. Bake 16 - 25 minutes depending on their thickness/size or until cooked through (internal temperature 165 - 174 degrees F.).
10. Let the chicken sit 5 minutes before serving with the remaining honey mustard dressing.