Potato & Leek Gratin

Ingredients

• 3 garlic cloves, minced
• 1.2 kg floury potatoes, peeled and thinly sliced (2–3mm)
• salt and black pepper
• 3 leeks, trimmed and thinly sliced into rounds
• 1 tsp fresh thyme leaves
• 400 ml double cream
• 200 ml whole milk
• 40 g unsalted butter
• 0.25 tsp freshly grated nutmeg
• 100 g Gruyère cheese, grated
• 30 g parmesan, grated
• Crusty sourdough bread, to serve
• Dressed green salad, to serve

Method

1. Heat the oven to 180°C fan. Butter a large gratin dish generously.
2. Melt the butter in a frying pan over medium heat. Add the leeks with a pinch of salt and cook for 8 minutes, stirring now and then, until soft, silky and just starting to colour at the edges. Stir in the garlic and thyme and cook for 1 minute more until fragrant. Slide off the heat.
3. Warm the cream, milk and nutmeg together in a saucepan over a low heat until just steaming and wisping at the edges — do not let it boil. Season generously with salt and plenty of black pepper.
4. Layer a third of the potato slices in the gratin dish, overlapping like roof tiles. Scatter over half the leeks, then a third of the combined cheeses. Repeat with another layer of potatoes, the rest of the leeks and another third of the cheese. Finish with a final layer of potatoes, fanned neatly on top.
5. Pour the warm cream mixture slowly and evenly over the top, letting it seep down through the layers. Scatter the remaining cheese across the surface.
6. Cover tightly with foil and bake for 50 minutes. Remove the foil and bake for a further 25–30 minutes, until the top is deeply golden and bubbling at the edges and a knife slides through the potatoes with no resistance.
7. Rest the gratin for 10 minutes before serving — the layers settle and hold together when you spoon them out.
8. Finish with a squeeze of lemon over the top and a scattering of fresh parsley just before bringing it to the table.