Preheat and prep: Heat your oven to 400°F (200°C). Lightly grease a 9x9-inch or similar baking dish.

Cook the cauliflower: Steam the cauliflower florets until very tender, about 10–12 minutes. Drain well and let steam off in the colander to remove excess moisture.

Make the mash: Blend or mash the cauliflower with butter, heavy cream, salt, and pepper until smooth. Stir in cheese and the egg yolk if using. Taste and adjust seasoning. Set aside.

Sauté aromatics: In a large skillet, warm oil over medium heat. Add onion, celery, and carrots (if using). Cook 5–6 minutes until softened. Stir in garlic and mushrooms; cook 2–3 minutes.

Brown the meat: Add ground lamb or beef. Season with salt and pepper. Cook, breaking it up, until browned and no longer pink. Spoon off excess fat if needed.

Build the sauce: Stir in tomato paste and cook 1 minute. Add worcestershire or coconut aminos, thyme, and rosemary. Pour in stock, starting with 1/2 cup.

Thicken (optional): If you like a thicker filling, sprinkle 1–2 tablespoons almond flour over the meat and stir, or whisk a tiny pinch of xanthan gum into the stock before adding. Simmer 3–4 minutes until slightly reduced and glossy. Taste and adjust salt and pepper.

Assemble: Spread the meat mixture evenly in the baking dish. Dollop the cauliflower mash on top and smooth with a spatula. Use a fork to create ridges for browning.

Bake: Bake 18–22 minutes until the top is lightly golden and the edges bubble. For extra color, broil 1–2 minutes, watching closely.

Rest and serve: Let the pie rest 10 minutes so the layers set. Sprinkle with parsley. Serve warm.