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, 20-25 minutes.

Meanwhile, halve, peel, and mince shallot. Strip 1 tsp rosemary leaves from stems (2 tsp for 4 servings); 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, 3-5 minutes per side. Transfer to a cutting board and set aside to rest.

To same pan over medium heat, 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, 30-60 seconds. Stir in stock concentrate and ¼ cup water (⅓ cup for 4 servings). Cook until thick and glossy, 2-3 minutes. (TIP: Add a splash of water if sauce is too thick.) Turn off heat; stir in 1 TBSP butter (2 TBSP for 4). Season with salt and pepper.

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

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