Preheat oven 180c fan.
Pour in 400ml double cream, 400ml milk and 3 crushed garlic cloves into a large saucepan and bring to a simmer.
Add a sprig of fresh thyme and a pinch of nutmeg.
Slice 10 large potatoes very finely, add them to the cream and simmer for 10 mins until just cooked.
Gently stir to separate the potato and stop it from sticking to the bottom of the saucepan.
Remove the potatoes with a slotted spoon and place them in a wide shallow ovenproof dish.
Pour over the garlic-infused cream.
Scatter over 100g grated gruyère cheese.
Oven bake for 30 to 40 mins until the potatoes are soft and browned.
Brown for 2 minutes under the grill.