In a medium bowl, mix together buttermilk, dijon mustard, honey, chili powder, salt, and pepper. Make sure honey is well incorporated and not clumpy. Set about 1 cup of the mixture aside for use later.
Spread out panko bread crumbs in a large plate.
Dip the chicken in the mixture and coat well. Then dredge (you may have to just pat it on) the chicken into the panko bread crumbs.
Cover the chicken and refrigerate for 15 minutes.
Preheat your oven to 425 F. Place a roasting rack in the oven for 5 minutes to get nice and hot.
Place chicken on rack and roast for about 1 & 1/2 to 2 hours, when internal temperature of chicken is 170 F. I'd recommend flipping the bird halfway through so the crust doesn't get overdone on one side.
Let rest for about 10 minutes after taking out of the oven and carve. Heat up the reserved cup of batter/sauce in the microwave for about 1-2 minutes, or until thick. Top chicken with sauce and serve on a plate with whatever sides you like!