Adjust racks to top and middle positions and preheat oven to 425 degrees. Wash and dry produce.

Trim, peel, and cut carrots on a diagonal into ½-inch-thick pieces.

Toss carrots on a baking sheet with a large drizzle of oil; season with salt and pepper. Roast on middle rack until tender, 25-30 minutes.

Dice potatoes into ½-inch pieces. Roughly chop parsley.

Place potatoes in a medium pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, 15-20 minutes. Reserve 1 cup potato cooking liquid (2 cups for 4 servings).

Drain and return potatoes to pot. Keep covered off heat until ready to mash.

In a large bowl, gently combine beef*, panko, half the onion and garlic spread, half the parsley, salt (we used ¾ tsp; 1½ tsp for 4 servings), and pepper. Form beef mixture into two 1-inch-tall loaves (four loaves for 4 servings); place on a second baking sheet.

Roast meatloaves on top rack until browned and mostly cooked through, 16 minutes.

Meanwhile, place 1 TBSP butter (2 TBSP for 4 servings) in a small microwave-safe bowl; microwave until melted, 30-60 seconds. Stir in remaining onion and garlic spread and ketchup.

Once meatloaves have cooked 16 minutes, remove sheet from oven. Spoon onion garlic glaze over meatloaves.

Return to top rack until meatloaves are cooked through and glaze is tacky, 2-4 minutes more.

Add sour cream and 1 TBSP butter (2 TBSP for 4 servings) to potatoes; mash with a potato masher or fork until smooth, adding splashes of reserved potato cooking liquid as needed. Season with salt and pepper.

Divide meatloaves, mashed potatoes, and roasted carrots between plates in separate sections. Sprinkle everything with remaining parsley and serve.