Adjust rack to middle position (middle and top positions for 4 servings) and preheat oven to 425 degrees. Bring a medium pot of salted water to a boil. Wash and dry produce.

Trim, peel, and halve carrots lengthwise; cut crosswise into 2-inch-long pieces. Trim and thinly slice scallions, separating whites from greens. Peel and mince or grate garlic. Zest and quarter lemon.

In a small bowl, combine panko, Parmesan, paprika, a large drizzle of olive oil, a pinch of chili powder, salt, and pepper.

Pat chicken* dry with paper towels; season all over with salt and pepper. Place on one side of a baking sheet. (For 4 servings, spread out across entire sheet.)

Spread tops of chicken with sour cream. Mound with panko mixture, pressing to adhere (no need to coat the undersides).

Toss carrots on opposite side of sheet from chicken with a large drizzle of olive oil, salt, and pepper. (For 4 servings, toss carrots on a second sheet.)

Roast on middle rack until chicken is cooked through and carrots are browned and tender, 15-20 minutes. (For 4, roast chicken on middle rack and carrots on top rack.)

Transfer chicken to a plate to rest. TIP: If carrots are done before chicken, remove from sheet and continue roasting chicken.

While chicken and carrots roast, add couscous to pot with boiling water. Cook until tender, 6-8 minutes. Drain thoroughly.

Melt 2 TBSP butter (3 TBSP for 4 servings) in empty pot over medium heat. Add scallion whites and garlic; cook until softened, 1 minute.

Return cooked couscous to pot and stir until coated. Season with salt and pepper to taste.

Once carrots are done roasting, carefully toss with lemon zest and a squeeze of lemon juice to taste.

Divide chicken, carrots, and couscous between plates. Garnish chicken with scallion greens. Serve with any remaining lemon wedges on the side.