Oven craft
Potato gratin, all the way through
A golden lid is only half the job. Thin layers and a gentle bake give the centre the attention it deserves.
THE PAYOFFTender potato layers under a golden top
TAKE IT STEP BY STEP
The method.
Make the layers even
Heat the oven to 180°C conventional / 160°C fan. Butter the dish. Slice the potatoes about 2 mm thick. Use a mandoline guard if you have one, or take your time with a knife. Even slices matter more than perfect circles.
Keep the starch
Slice close to assembly time and do not rinse the cut potatoes: their surface starch helps thicken the dairy. Warm the milk, cream, garlic, salt and a little pepper in a saucepan until steaming; do not boil hard.
Build a shallow dish
Arrange overlapping potato layers in the buttered dish, keeping the overall depth no more than about 4 cm. Pour over the warm dairy. It should settle between the slices and come close to the top layer without drowning it. Do not fill the dish to the rim.
Bake for tenderness first
Cover with foil and bake for 50–60 minutes. Push a thin knife into the centre: it should pass through the layers with little resistance. If the potatoes are still firm, cover again and continue in 10-minute stages. Thickness and dish material change the timing.
Brown, then rest
Remove the foil and bake for another 15–25 minutes, until the surface is golden and the cream bubbles gently around the edges. Rest for 15 minutes before serving. Expect soft, creamy layers, rather than a rigid stack.
WHEN IT GOES SIDEWAYS
A small fix.
The top is dark but the centre is firm
Cover loosely with foil and continue baking gently until a knife slips through the centre. Move the dish lower in the oven if the top is catching.
There is lots of loose liquid
Check the potatoes are tender, then give the dish its resting time. For the next batch, keep the layers shallow and avoid rinsing away the starch.
It looks greasy
An overly fierce bake can separate the dairy. Lower the heat, and avoid adding large amounts of cheese or extra butter to this cream-based version.
Serve with a sharp green salad or a simply cooked main. For a cheese finish, scatter a modest handful of grated Gruyère on top when the foil comes off.