Preheat oven to 400 degrees F. Grease a large baking sheet with sides or a 9 x 13-inch baking pan.

In the bowl of a food processor pulse the pecans until finely chopped or place them in a ziploc bag, set them on a flat surface, cover with a kitchen towel and pound into crumbs with a meat mallet. Pour them into a wide, shallow bowl.

In a small bowl whisk the mayo and mustard together.

Season the chicken with salt and pepper. Using a spoon or pastry brush coat the tops and sides of the chicken with the mayo mixture. Dredge in the pecans, patting them on to help them stick. Place on the baking sheet pecan side up.

Bake 25 minutes or until cooked through. Internal temperature on a meat thermometer should read 164 - 175 F. If the pecans start to get too dark cover the pan with foil.

Meanwhile whisk the maple syrup, mustard, vinegar and mayonnaise together until well combined. Add a couple dashes of salt and pepper. Refrigerate.

Let the chicken sit 5 minutes before serving. Drizzle the sauce over it or serve on the side for dunking.