Prep ingredients: Preheat oven to 450°F with a rack in the center. Finely chop onion. Slice 2 large garlic cloves. Peel sweet potatoes, then cut into 1-inch pieces. Scrub and trim carrots, then cut into ½-inch pieces. Pick and coarsely chop 1½ teaspoons thyme leaves. In a liquid measuring cup, stir to combine broth concentrate with ¾ cup water.

Cook garlic butter, onion: Melt 2 tablespoons butter in a medium skillet over medium heat. Add half of the garlic and cook, stirring occasionally, until butter is lightly browned and golden, 2–3 minutes. Transfer to a small bowl. Add onions and 1 tablespoon oil to skillet. Cook over medium-high, stirring, until onions are softened, 4–5 minutes. Transfer ¾ of the onions to a medium bowl. Set skillet aside.

Form & bake meatloaf: Bring a medium saucepan of salted water to a boil. To onions in bowl, add beef, panko, ¾ chopped thyme, 1 large egg, 1 teaspoon salt, and pepper; knead to combine. Form into a 6-inch meatloaf and place on a rimmed baking sheet; drizzle with oil. Bake on center oven rack until browned, firm to touch, and reaches an internal temperature of 165°F, about 20 minutes.

Cook peas & carrots: Meanwhile, add carrots to boiling water and cook until tender, 6–8 minutes. Add peas and cook, 2 minutes more. Use a slotted spoon to transfer veggies to a medium bowl. Add 1 tablespoon butter and toss to coat until butter is melted. Cover to keep warm. Return pot of water to a boil.

Make mashed potatoes: Add sweet potatoes and remaining sliced garlic to pot with boiling water. Cook over high until potatoes are tender when pierced with a knife, about 10 minutes. Drain potatoes and garlic, then return to pot over low heat. Add cream cheese and ¼ cup milk or water and mash with a potato masher or fork until smooth. Season with salt. Remove from heat and stir in garlic butter.

Make gravy & serve: Meanwhile, add remaining chopped thyme and 1 tablespoon flour to cooked onions in skillet over medium-high. Cook until fragrant, about 1 minute. Add broth and simmer until thickened, about 4 minutes. Slice meatloaf crosswise. Serve with mashed potatoes and peas and carrots alongside. Spoon gravy over top. Enjoy!