Heat the oven to 200C/180C fan/gas 6. Tip the cream, milk, garlic and thyme into a large pan and bring to a simmer. Remove from the heat and leave to infuse for 15 mins. Strain, discarding the garlic and thyme. Grate in some nutmeg and season to taste.

Toss the leek, brussels sprouts and carrot together in a bowl. Arrange half the potatoes in the bottom of a medium baking dish, overlapping the slices. Top with the veg mixture and half the cream mixture, then arrange the remaining potatoes on top. Pour over the remaining cream mixture, then scatter over the cheese. Bake for 50 mins-1 hr, covering with foil if it starts to brown too quickly. Leave to rest for 10 mins before serving.