Position a rack in the upper third of the oven; preheat to 475 degrees F. Brush a rimmed baking sheet with 1 tablespoon olive oil. Add the chicken skin-side up; season with salt, pepper and 1/2 teaspoon chili powder. Arrange the sweet potatoes around the chicken; season with salt and pepper. Drizzle the chicken and sweet potatoes with 1 tablespoon olive oil. Roast until the chicken is lightly browned and the sweet potatoes are just tender, 25 to 30 minutes.
Meanwhile, combine the mustard, 1 tablespoon hot sauce and the remaining 1/2 teaspoon chili powder in a small bowl. Toss the panko, melted butter, remaining 1 teaspoon hot sauce and a pinch of salt in another small bowl.
Remove the baking sheet from the oven and spread the mustard mixture on top of each chicken breast. Top with the panko, lightly pressing to adhere. Move the chicken and sweet potatoes to one side of the pan. Mound the kale on the other side; toss with the remaining 1 tablespoon olive oil and season with salt and pepper.
Roast until a thermometer inserted into the thickest part of the chicken registers 165 degrees F and the kale is crisp on top, about 15 minutes.
Photograph by Bobbi Lin