How to make Potato Gratin

Step-by-step

1. Step 1

   Prepare the potatoes as follows: potatoes sliced 2–3 mm. Keep the pieces even because this dish depends on all potatoes finishing at the same time.

   Look for: Potatoes are uniform: potatoes sliced 2–3 mm. Tip: Use a ruler once, then copy that size by eye. Avoid: Uneven cutting is the quickest route to raw centres and burnt edges.

2. Step 2

   Use a 25 x 18 cm baking dish. Bring the cooking surface or oven to 180°C before the potatoes go in.

   Look for: The 25 x 18 cm baking dish is hot enough that the potato starts cooking immediately. Tip: Preheat longer than you think for cast iron, trays and waffle irons. Avoid: Adding potatoes to a cold pan or oven makes them absorb fat before browning.

3. Step 3

   Cook the potatoes gently at first so the centres soften before the outside gets too dark. For layered dishes, keep the slices flat and pressed; for fried dishes, leave them still until the first crust forms.

   Look for: Centres begin to yield while the outside is only lightly coloured. Tip: Listen for a steady sizzle rather than aggressive spitting. Avoid: High heat from the start gives dark surfaces with hard centres.

4. Step 4

   Add the fat, seasoning and aromatics at the point they will flavour the potato without burning: delicate herbs and garlic usually go in after the first browning, while spices need enough fat to bloom.

   Look for: Aromatics smell fragrant and the fat is tinted or glossy, not burnt. Tip: If spices are sticking, add a spoon of water, stock or oil depending on the dish. Avoid: Raw garlic or scorched spices make the whole dish taste harsh.

5. Step 5

   Continue until the dish shows its correct finish: cream, milk and cheese should bubble into a browned lid. Adjust the heat if the outside colours before the centre is tender.

   Look for: Cream, milk and cheese should bubble into a browned lid. Tip: Use a knife, skewer or spatula test rather than relying on the clock alone. Avoid: Stopping at pale beige usually means the potato has not developed enough flavour.

6. Step 6

   Rest briefly if layered, baked or mashed; serve immediately if fried or crisp. Taste for salt at the end because potatoes mute seasoning as they cool.

   Look for: Texture is settled but still hot; crisp dishes remain dry on the surface. Tip: A final pinch of salt or fresh herbs should land just before serving. Avoid: Covering crisp potatoes tightly traps steam and softens them.