Preheat the Oven and Fat: Place your chosen fat (goose fat, duck fat, or oil) into a large, sturdy roasting tin. Pop it into the oven and preheat to 200°C (180°C Fan, Gas Mark 6). Getting the fat screaming hot is essential.

Prepare the Potatoes: Peel the potatoes and chop them into evenly-sized pieces, roughly the size of a golf ball. Don't worry about perfect shapes; irregular edges are your friend here. Rinse them under cold water to remove some of the excess starch.

Parboil the Potatoes: Place the potatoes in a large saucepan and cover with cold water. Add the 2 teaspoons of fine sea salt. Bring to the boil and let them bubble away for 10-12 minutes, or until the outside is soft but the centre still has a definite bite. You should be able to pierce the edge with a fork easily.

Drain and Steam Dry: Drain the potatoes carefully in a colander. Leave them to sit in the colander for 2-3 minutes to steam dry. This step helps remove surface moisture, which is the enemy of crispiness.

Rough Them Up: This is the secret to a craggy crust! With the potatoes still in the colander, give them a good, firm shake (put the lid on the pan and shake them in there if your colander feels flimsy). The aim is to scuff up the edges and create a rough, starchy paste on the outside of each potato.

Get Roasting: Carefully remove the hot roasting tin from the oven. The fat should be shimmering. I find that using a long-handled metal spoon to gently lower the potatoes into the hot fat one by one is the safest way to avoid splashes. Gently turn each potato to coat it in the hot fat.

First Roast: Place the tin back in the hot oven and roast for 25-30 minutes. By this point, they should be starting to turn a light golden colour.

Turn and Finish Roasting: Remove the tin from the oven. Use tongs to turn each potato over. If you're adding rosemary, thyme, or garlic, now is the time to toss them in. Return the tin to the oven and roast for another 25-35 minutes, or until they are a deep golden-brown, wonderfully crisp, and audibly crunchy.

Serve Immediately: Remove the potatoes from the tin and drain them for a moment on a plate lined with kitchen paper. Sprinkle generously with the flaky sea salt and black pepper, and serve straight away while they're piping hot.