Adjust racks to top and middle positions and preheat oven to 450 degrees. Wash and dry all produce. Dice potatoes into ½-inch pieces. Toss on a baking sheet with a drizzle of olive oil, salt, and pepper. Roast on top rack, tossing halfway through, until browned and tender, 22-25 minutes.

Meanwhile, halve, peel, and mince shallot. Strip 1 tsp rosemary leaves from stems (2 tsp for 4 servings); discard stems and finely chop leaves. Zest and quarter lemon. Cut broccoli florets into 1-inch pieces, if necessary; toss on a second baking sheet with a drizzle of oil, salt, and pepper. Roast on middle rack until browned and tender, 12-15 minutes.

While broccoli roasts, pat chicken dry with paper towels; season all over with salt and pepper. Heat a drizzle of olive oil in a large pan over mediumhigh heat. Add chicken and cook until browned and cooked through, 5-7 minutes per side. Remove from pan and set aside to rest.

Lower heat under pan to medium; add shallot, chopped rosemary, and a drizzle of olive oil. Cook, stirring, until softened, 2-3 minutes. Stir in vinegar and jam. Simmer until syrupy, 30 seconds to 1 minute. Stir in stock concentrate and ¼ cup water (⅓ cup for 4 servings). Let reduce until thick and glossy, 2-3 minutes. (TIP: Add a splash of water if mixture is too thick.) Turn off heat; stir in 1 TBSP butter (2 TBSP butter for 4). Season with salt and pepper.

Once broccoli is done, remove from oven and toss with lemon zest to taste.

Thinly slice chicken crosswise. Divide chicken, potatoes, and broccoli between plates. Drizzle chicken with sauce. Serve with lemon wedges on the side.