• Adjust racks to top and middle positions and preheat oven to 425 degrees. Wash and dry produce. • Cut potatoes into 1/2-inch-thick wedges. Halve, peel, and thinly slice onion. Mince a few slices until you have 2 TBSP (4 TBSP for 4 servings). Cut broccoli florets into bite-size pieces if necessary. (Save potatoes for another use.)

• Toss potatoes on a baking sheet with a drizzle of oil, salt, and pepper. • Roast on top rack until browned and tender, 20-25 minutes. Swap in broccoli for potatoes. Roast until browned and tender, 12-15 minutes.

• Meanwhile, in a large bowl, gently combine beef*, panko, garlic powder, stock concentrate, minced onion, half the ketchup, salt (we used 1/2 tsp; 1 tsp for 4 servings), and pepper. • Form beef mixture into two 1-inch-tall loaves (four loaves for 4); place on a second baking sheet. Brush tops of meatloaves with remaining ketchup. • Roast on middle rack until cooked through, 15-20 minutes.

• While potatoes and meatloaves cook, heat a large drizzle of oil in a large, preferably nonstick, pan over medium-high heat. Add sliced onion and cook, stirring occasionally, until browned and softened, 8-10 minutes. • Add 1 tsp sugar (2 tsp for 4 servings) and a splash of water. Cook, adding more splashes of water as necessary, until onion is caramelized and jammy, 2-3 minutes more. Season with salt and pepper. • Turn off heat; transfer onion to a small bowl. Wipe out pan.

• Heat 1 TBSP butter in same pan over medium heat. Add bread and toast until golden brown, 2-3 minutes per side (add more butter and work in batches as needed). • While bread toasts, in a second small bowl, combine horseradish sauce, mayonnaise, and half the mustard (all for 4 servings). Set aside.

• Lay toasted bread out on a cutting board. Spread half the bread slices with caramelized onion; spread remaining bread slices with sauce (save some for serving). • Cut each meatloaf crosswise into four slices; fan out slices over bread topped with caramelized onion. Close sandwiches and cut in half. • Divide sandwiches and potato wedges between plates. Serve with remaining sauce on the side for dipping. Ground Beef is fully cooked when internal temperature reaches 160º.