Preheat the oven (180 degrees C w/ fan).
Peel the potatoes & cut them in slices of about 2-3 mm.
Mix milk & cream, add salt & pepper and nutmeg from a nutmeg grater.
Put the potatoes & the milk-mix in a pot & bring it to a boil.
Afterwards let it simmer for about 10 min.
Grease the casserole bowls w/ butter.
Cut in half the clove of garlic & rub the garlic in the buttered casserole bowls.
Optional: Grate the Gruyère.
Fill the casserole bowls evenly w/ the hot potato-milk-mix.
Optional: Add the grated Gruyere to the bowls (mix in & on top).
Let it bake in the oven for about 30 min.