Steam the cauliflower: Place the cauliflower florets in a large steamer basket over boiling water, cover, and steam for 12–15 minutes. You'll know they're ready when a fork slides through the thickest stem with no resistance — the florets should smell sweet and nutty, not sulphurous.

Make the cauliflower mash: Transfer the steamed cauliflower to a clean tea towel (or use a salad spinner) and squeeze out as much water as you possibly can. This is the single most important step — you're looking for the florets to feel dry to the touch. Return them to the pot, add the butter, double cream, and half the grated cheddar, then mash with a potato masher until smooth and velvety. Season with salt and pepper. Set aside.

Brown the mince: Heat the olive oil in a large, oven-safe frying pan or skillet over medium-high heat. Add the minced lamb and let it sit undisturbed for 3–4 minutes — listen for a deep sizzle that tells you the pan is hot enough. Break it apart with a wooden spoon and continue cooking until every piece is deeply browned and no pink remains. The kitchen should smell rich and savoury at this point.

Sweat the vegetables: Reduce the heat to medium. Add the diced onion, carrot, and celery to the pan with the lamb. Cook for 8–10 minutes, stirring occasionally, until the onions turn translucent and the carrots soften. You should see the vegetables glistening with fat and the edges of the onion starting to catch golden — that's flavour building.

Build the sauce: Stir in the minced garlic and tomato purée, cooking for 1 minute until the purée darkens to a rusty red and smells intensely tomatoey. Sprinkle over the dried thyme and rosemary, then pour in the beef stock. Bring everything to a gentle bubble — you'll see small, lazy bubbles breaking the surface, not a furious boil.

Simmer the filling: Reduce the heat to low and let the filling simmer uncovered for 15–20 minutes. Stir occasionally to prevent sticking. The liquid should reduce by about half, leaving a thick, glossy sauce that coats the back of a spoon. Taste and adjust seasoning — it should be deeply savoury with a hint of herbaceousness from the thyme.

Assemble the pie: Preheat your oven to 200°C (fan-assisted). If your pan isn't oven-safe, transfer the filling to a 20cm x 25cm baking dish. Spoon the cauliflower mash over the top in dollops, then spread it gently into an even layer — don't press it down or it'll mix into the filling. Use a fork to create decorative peaks across the surface; these will crisp up beautifully.

Bake until golden: Sprinkle the remaining grated cheddar over the top of the mash. Bake for 20–25 minutes, until the filling is bubbling up around the edges (you'll see and hear it) and the cauliflower topping is golden brown with darker spots on the peaks. Let the pie rest on the counter for 10 minutes before serving — this allows the filling to set so it doesn't flood your plate.