Hearty Meat and Vegetable Shepherd's Pie

1. Prepare Mashed Potatoes

Peel and cut 3.5 pounds of russet potatoes into 1-inch pieces, then rinse them under cold water until the water runs clear. In a large saucepan, cover the potatoes with cold water, add a generous pinch of kosher salt, and bring to a boil. Cook until the potatoes are tender, about 10-15 minutes. Drain them well and rinse with hot water to ensure they stay fluffy. Mash the potatoes with 6 tablespoons of cubed unsalted butter until smooth, then cover with plastic wrap to keep them warm and prevent a skin from forming.

2. Prepare Meat Sauce

In a measuring cup, combine 1.5 cups of low-sodium chicken stock with 2 packets of unflavored gelatin and set aside to hydrate. Heat 2 tablespoons of vegetable oil in a large Dutch oven over medium-high heat. Add half of the ground beef and cook, breaking it up with a potato masher or whisk, until well browned, about 6-8 minutes. Add the remaining ground beef and cook for about 3 more minutes until it's no longer pink.

3. Cook Vegetables

Stir in the diced onion, carrots, celery, and minced garlic, cooking until the vegetables are softened, approximately 4 minutes.

4. Add Tomato Paste and Wine

Add 2 tablespoons of tomato paste and cook for another minute to caramelize slightly. Pour in 1 cup of dry red wine and let it simmer until almost fully evaporated.

5. Simmer Meat Sauce

Stir in the prepared chicken stock with gelatin, 2 sprigs of thyme, 1 bay leaf, 1 tablespoon of Worcestershire sauce, and 1 teaspoon of Marmite. Sprinkle 2 tablespoons of all-purpose flour over the mixture and stir well to incorporate. Let the sauce simmer for about 20 minutes until it's thickened and reduced. Remove the thyme sprigs and bay leaf, and stir in 8 ounces of frozen peas. Season with kosher salt and freshly ground black pepper to taste.

6. Preheat Oven and Heat Cream

Preheat your oven to 425°F (220°C). Heat 1.5 cups of heavy cream in a large saucepan until warm, then mix it into the mashed potatoes until they are smooth and creamy.

7. Assemble Shepherd's Pie

Spread the meat sauce evenly in a 9x13-inch baking dish placed on a foil-lined rimmed baking sheet to catch any drips. Top with the mashed potatoes, smoothing them out with a spatula and creating a dappled pattern for texture. If desired, sprinkle with grated Parmigiano-Reggiano cheese.

8. Bake Shepherd's Pie

Bake the shepherd's pie in the preheated oven for about 20 minutes until the top is browned and crisp. Let it stand for 15-20 minutes before serving to allow the flavors to meld and the pie to set.