Preheat the oven to 220C/425F (fan).
Peel the potatoes and chop them into chunky pieces a little bigger than a ping pong ball (approx 2 inches/5cm across).
Place in a pan and cover with cold water. Place on the hob on a high heat and bring to the boil, then turn down the heat and simmer for 8-9 minutes - until softened at the edges.* Tip 1
Meanwhile, place the lard or (goose fat if using) in a large roasting tin and place in the oven for 10 minutes until shimmering hot.
Drain the potatoes in a colander *Tip 2, and give them a good shake to really roughen up the edges. Don't worry if a few break apart and they look overly fluffy. The more fluffy they are, the better they'll absorb the fat and the crispier they'll be.
Carefully place the potatoes - using tongs - in the baking tin with the hot fat. Turn them over once to coat in the fat and then place them in the oven.
Cook for 30-35 minutes, turning once or twice in the last 15 minutes of cooking, until golden brown and crispy.
Remove from the roasting tin and serve topped with a sprinkling of Maldon salt and some fresh thyme leaves.
