Step 1

Heat broiler to high. Wash and dry produce. Dice potatoes into ½-inch pieces. Strip thyme leaves from stems; roughly chop leaves. Trim, peel, and halve carrot lengthwise; slice crosswise into ¼-inch-thick half-moons. Finely dice celery. Halve, peel, and finely chop onion.

Step 2

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. Drain and return potatoes to pot. Mash potatoes with sour cream, 2 TBSP butter (3 TBSP for 4 servings), and 1 tsp chopped thyme until smooth and creamy, adding splashes of water as needed. Season generously with salt and pepper. Keep covered off heat until ready to serve.

Step 3

While potatoes cook, heat a drizzle of oil in a medium, preferably ovenproof, pan (for 4 servings, use a large, preferably ovenproof, pan) over medium-high heat. Add carrot; season with salt and pepper. Cook, stirring, until slightly softened, 2-3 minutes. Add celery, onion, and a large drizzle of oil; season with salt and pepper. Cook, stirring, until veggies are just tender, 5-7 minutes. TIP: If veggies begin to brown too quickly, add a splash of water. Stir in garlic powder and 2 tsp chopped thyme; cook until fragrant, 30 seconds.

Step 4

Add beef* to pan with veggies and season with salt and pepper. Cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes. Add flour; cook, stirring, until thoroughly combined, 1 minute.

Step 5

Add half the crushed tomatoes (all for 4 servings) and ½ cup water into pan with beef mixture. Stir in stock concentrates and bring to a boil. Cook until mixture is very thick, 1-2 minutes. Turn off heat. Taste and season with salt and pepper. TIP: If your pan isn’t ovenproof, transfer mixture now to a baking dish.

Step 6

Top beef filling with an even layer of mashed potatoes, leaving a gap around edge of pan. Evenly sprinkle with cheddar. Broil until browned, 3-4 minutes. TIP: Watch carefully to avoid burning. Serve directly from pan.