Begin roasting potatoes. Heat a conventional oven to 425°F (220°C). Toss potatoes with 1 tablespoon oil, ½ teaspoon salt, and half the pepper. Spread on a large lined tray and roast for 15 minutes. Use a second tray if the potatoes cannot fit in a single layer.

Add the broccoli. Toss broccoli with ½ tablespoon oil and spread beside the potatoes, turning the potatoes at the same time. Roast for about 15–20 minutes more, until the potatoes are tender and broccoli edges have some color. Remove finished broccoli earlier if needed.

Cook the chicken in batches. Pat chicken dry and season with garlic powder, remaining salt, and remaining pepper. Heat the remaining ½ tablespoon oil in the skillet. Cook the chicken in two batches over medium-high heat for about 6–9 minutes per batch, turning and checking several thick pieces for 165°F (74°C).

Coat with buffalo sauce. Return cooked chicken to the pan, reduce the heat, and add hot pepper sauce and butter. Toss for about 1 minute, just until the butter melts and the sauce coats the chicken. Remove from the heat rather than boiling the sauce until it turns sticky and concentrated.

Mix the cool topping. Stir yogurt, lemon juice, dill, onion powder, and chives together. Divide into four small pots. Prepare celery and carrot with clean utensils and keep them refrigerated. Divide potatoes, broccoli, and chicken evenly among four bowls.

Serve or pack safely. For immediate serving, add the celery, carrot, and yogurt. For meal prep, chill the cooked components promptly in shallow containers and keep the cold toppings separate. Reheat chicken, potatoes, and broccoli to 165°F (74°C) before adding the chilled topping.