Preheat oven to 400°F. Place chicken thighs, 1 teaspoon onion powder, ½ teaspoon salt and ¼ teaspoon each black pepper and cayenne in a medium bowl; toss until the chicken is evenly coated.

Heat 1 tablespoon oil in a large cast-iron skillet over high heat. Add the chicken skin-side down; cook, undisturbed, until golden brown and crispy, about 4 minutes. Transfer to a plate.

Reduce heat to medium-high; add potatoes, carrots, shallots, 1 tablespoon butter, 1 teaspoon garlic and ¼ teaspoon salt. Cook, stirring occasionally, until the vegetables are lightly browned and softened, about 10 minutes. Return the chicken and any accumulated juices to the pan, nestling the chicken skin-side up in the vegetable mixture. Roast until a thermometer inserted into the thickest portion of chicken registers 165°F and the vegetables are fork-tender, about 15 minutes.

Meanwhile, combine 2 tablespoons hot honey, 2 teaspoons Sriracha, ¼ teaspoon orange zest and the remaining 3 tablespoons butter, 1 teaspoon garlic, ¼ teaspoon each black pepper and cayenne and ⅛ teaspoon salt in a small saucepan. Cook over low heat, stirring occasionally, until thickened and a glaze forms, 4 to 6 minutes. Remove from heat and cover to keep warm.

Remove the chicken from the oven; brush with the hot honey mixture. Roast until the glaze is glossy, about 5 minutes. Garnish with parsley leaves, if desired.