Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 425 degrees. Wash and dry produce.

Trim, peel, and cut parsnips on a diagonal into ½-inch pieces. Trim, peel, and cut carrots on a diagonal into ½-inch pieces. Cut potatoes into ½-inch-thick wedges. Halve, peel, and cut half the onion into ½-inch wedges (you'll finish prepping the remaining onion in Step 4).

Toss parsnips, carrots, potatoes, and onion wedges on one side of a baking sheet with a drizzle of oil, salt, and pepper (for 4 servings, spread veggies out across entire sheet). TIP: Line sheet with foil first for easier cleanup! 

Roast on top rack for 10 minutes (you'll add more to the sheet then).

While veggies roast, in a large bowl, combine beef*, panko, ketchup, garlic powder, 1 tsp salt (2 tsp for 4 servings), and pepper. 

Form mixture into two 1-inch-tall loaves (four loaves for 4).

Once veggies have roasted 10 minutes, remove sheet from oven. Carefully place meatloaves on opposite side of sheet (for 4, leave veggies roasting; place meatloaves on a second baking sheet). Return to top rack and roast until veggies are browned and tender and meatloaves are cooked through, 17-20 minutes. (For 4, roast meatloaves on middle rack, swapping rack positions with veggies halfway through.)

Meanwhile, finely dice remaining onion.

Melt 1 TBSP butter (2 TBSP for 4 servings) in a medium pan over medium heat. Add diced onion and 1 tsp sugar (2 tsp for 4); season with salt. Cook, stirring occasionally, until lightly browned and softened, 7-9 minutes. TIP: If onion begins to brown too quickly, lower heat and add a splash of water.

Sprinkle flour over onion mixture; cook, whisking constantly, until flour is lightly browned, 1-2 minutes. 

Slowly whisk 1 cup water (1½ cups for 4 servings) and stock concentrate into pan. Cook, whisking constantly, until thickened, 3-5 minutes.

Remove from heat; whisk in sour cream. Taste and season with salt and pepper. TIP: If gravy seems too thick, whisk in a splash of water.

Divide meatloaves and veggies between plates in separate sections. Top meatloaves with gravy and serve.