Peel and dice the potato, then place in a pot with the cauliflower florets and cover with water.
Bring to a boil and cook for 12-15 minutes until very tender; drain well.
Mash the potato and cauliflower with the ghee and half of the sea salt until smooth and velvety.
While the vegetables boil, preheat your oven to 400°F (200°C).
In a large oven-safe skillet over medium-high heat, brown the ground beef with the diced onion, breaking it up with a spatula.
Add the diced carrots and minced garlic, sautéing for 3-4 minutes until the vegetables begin to soften.
Stir in the tomato paste, bone broth, coconut aminos, thyme, remaining sea salt, and black pepper.
Simmer the mixture for 5-7 minutes until the sauce has thickened into a rich gravy, then stir in the frozen peas.
Spread the meat mixture into an even layer in the skillet (or transfer to a small baking dish).
Top with the root vegetable mash, smoothing it to the edges and using a fork to create decorative peaks.
Bake for 15-20 minutes, then broil for 2-3 minutes until the peaks are golden brown.