• Wash and dry produce. • Dice potatoes into 1⁄2-inch pieces; place in a large pot with enough salted water to cover by 2 inches. Bring to a boil and cook until tender, 15-20 minutes. • Reserve 1⁄2 cup potato cooking liquid, then drain and return potatoes to pot. • Keep covered off heat until ready to mash.

• While potatoes cook, trim and quarter mushrooms. (Skip if your mushrooms are pre-sliced!) Trim, peel, and finely dice carrots. Halve, peel, and dice half the onion (whole onion for 4 servings). Strip thyme leaves from stems.

• Heat a large drizzle of olive oil in a large, preferably ovenproof, pan over medium-high heat. Add mushrooms and a big pinch of salt. Cook, stirring occasionally, until lightly browned, 5 minutes. • Add another drizzle of olive oil, carrots, and onion; season with salt. Cook, stirring, until veggies are softened, 5-7 minutes more.

• Stir 1 TBSP butter (2 TBSP for 4 servings) into pan with veggies until melted, then add garlic powder, flour, and half the thyme (all for 4). Cook, stirring, 1 minute. • Stir in tomato paste until incorporated, 1 minute. • Add 3⁄4 cup water (1 cup for 4) and stock concentrates, scraping up any browned bits from bottom of pan. Bring to a boil, then reduce to a low simmer. Cook until thickened, 2-3 minutes. Season generously with salt and pepper. Turn off heat. TIP: If your pan isn’t ovenproof, transfer mixture now to a baking dish.

• Mash drained potatoes with sour cream, half the Monterey Jack (you’ll use the rest in the next step), and 2 TBSP butter (3 TBSP for 4 servings) until smooth and creamy, adding splashes of reserved potato cooking liquid as needed. Season with salt and pepper.

• Heat broiler to high. • Once filling has thickened, spoon mashed potatoes on top. Spread into an even layer, leaving a 1-inch border around edge of pan. • Sprinkle potatoes with remaining Monterey Jack.

• Broil until cheese is lightly browned, 3-4 minutes. TIP: Watch carefully to avoid burning. • Let rest at least 5 minutes, then divide between plates and serve.