Step 1: Bake the Potatoes

1. Preheat the oven to 400°F (200°C).
2. Scrub and dry the russet potatoes, then pierce them a few times with a fork.
3. Place them directly on the oven rack or on a baking sheet and bake for about 1 hour, or until the skins are crispy and the insides are soft.

Step 2: Make the Shepherd’s Pie Filling

1. While the potatoes bake, heat a skillet over medium heat and cook the ground beef or lamb until browned. Drain excess fat if necessary.
2. Add the diced onion, garlic, and carrots. Sauté for 5 minutes until softened.
3. Stir in the tomato paste, Worcestershire sauce, and beef broth. Let simmer for 5-7 minutes until slightly thickened.
4. Add the frozen peas, stir to combine, and remove from heat.

Step 3: Prepare the Mashed Potatoes

1. When the potatoes are done, let them cool slightly before slicing the tops off.
2. Scoop out some of the potato flesh, leaving a sturdy shell.
3. In a bowl, mash the scooped-out potato with butter, milk, salt, and pepper until smooth. Add more milk if needed for a creamy consistency.

Step 4: Assemble and Bake

1. Fill each potato shell with the shepherd’s pie filling.
2. Top with a layer of the mashed potatoes.
3. Sprinkle shredded cheddar cheese on top (if using).
4. Place under the broiler for 2-3 minutes until golden brown and bubbly.

Step 5: Serve and Enjoy

Let the potatoes cool slightly before serving. Enjoy as a hearty meal on its own or with a simple side salad.