Step 1

Heat oven to 190C/170C fan/gas 5.

Step 2

Tip 500ml double cream, 500ml milk and 3 garlic cloves into a large saucepan and bring to a simmer.

Step 3

Slice 8 large potatoes very finely, about 3-4mm, add them to the cream and simmer for 3 mins until just cooked.

Step 4

Gently stir to separate the potato and stop it sinking and catching on the bottom of the pan.

Step 5

Remove the potatoes with a slotted spoon and place in a wide shallow ovenproof dish so that they are about 5cm in depth.

Step 6

Pour over the garlic infused cream (discarding the garlic) – just enough to seep through the layers and leave a little moisture on the surface.

Step 7

Scatter over 100g grated gruyère cheese, if using, then bake for 30 mins until the potatoes are soft and browned – increase the heat for 5 mins if not brown enough.