Preheat your oven to 400°F (200°C). Scrub the russet potatoes clean, poke a few holes with a fork, and bake them directly on the oven rack for about 50-60 minutes, until tender when pierced.

In a large skillet over medium heat, brown the ground lamb or beef with diced onion and minced garlic. Cook until the meat is browned and the onions are translucent, about 8-10 minutes.

Stir in the frozen peas and carrots, tomato paste, and beef broth. Let the mixture simmer for about 10 minutes until the vegetables are tender and the sauce thickens up a bit.

Once the potatoes are baked and cool enough to handle, slice them in half lengthwise. Gently scoop out some of the flesh, creating a boat. Fill each potato half with the savory meat mixture, packing it well.

Spread a generous layer of prepared mashed potatoes over each stuffed potato. You can use a fork to create a crisscross pattern on top for added texture.

Place the stuffed potatoes in the oven at 375°F (190°C) for about 25-30 minutes, or until the tops are golden and slightly crispy.