Adjust racks to top and middle positions and preheat oven to 425 degrees. Wash and dry all produce. Halve and peel shallot. Grate one half with a grater into a medium bowl (use a large bowl for 4 servings); mince other half. Mince garlic. Strip thyme leaves from stems and roughly chop. Halve carrots lengthwise. Cut potato into 1/2-inch-thick wedges.

Toss carrots on one baking sheet with a drizzle of olive oil, salt, and pepper. Toss potato on a separate baking sheet with a drizzle of olive oil, salt, and pepper. Roast, flipping halfway through, until browned and tender, 25-30 minutes total (we’ll add more ingredients to sheet with the potato after 7 minutes).

Meanwhile, to bowl with grated shallot, add beef, garlic, 1/4 cup panko (1/2 cup for 4 servings), half the thyme, salt, and pepper (we used 3/4 tsp kosher salt; use 11/2 tsp for 4 servings). Gently combine, then shape mixture into two 1-inch-tall loaves (four for 4 servings).

Once potato has roasted 7 minutes, remove from oven, leaving carrots roasting. Push potato to one side of sheet. Place meatloaves on opposite side, then brush tops of loaves with half the ketchup (use all the ketchup for 4 servings). Return to oven and continue roasting until meatloaves are cooked through, 15-18 minutes more.

Meanwhile, melt 1/2 TBSP butter (1 TBSP for 4 servings) in a medium pan over medium heat. Add minced shallot and remaining thyme. Cook, stirring, until softened, 3-4 minutes. Sprinkle flour into pan, stirring vigorously to combine. Whisk in stock concentrate and 1/2 cup water (1 cup for 4 servings). Bring to a simmer and let bubble until thickened and saucy, 3-4 minutes. Season with salt and pepper.

Slice meatloaves crosswise. Divide meatloaves and veggies between plates. Spoon gravy over meatloaves and serve.