Gather the ingredients.
In a large saucepan over medium heat, bring the
potatoes, milk, and garlic to a gentle simmer.
Continue simmering the potatoes for 15 minutes,
until they just start to turn tender. Be very
careful not to overcook them as they need to hold
their shape for layering in the pan.
Preheat the oven to 350 F.
Drain the milk from the pan and add the heavy
cream, crème fraiche or sour cream, salt, pepper,
and nutmeg to the hot potatoes.
Heat the cream mixture to barely a simmer (a few
bubbles are fine but no more) for 10 to 15 minutes
until the potatoes are very tender but not falling
Butter a large baking dish and carefully lift the
potatoes into the dish and layer without breaking
them up too much.
Cover with the cream from the pan.
Sprinkle the Gruyere cheese over the potatoes (if
This is a great make-ahead side dish. Simply
refrigerate it for up to 1 day before the final
baking stage. To serve, bring it up to room
temperature, cover with foil, and put it into a
very hot oven as above.
For a restaurant-style serving, leave the gratin
to cool in the dish until cold then pop it into
the refrigerator for a few hours or overnight.
When ready, use a tart cutter for individual
portions and reheat by wrapping in foil and
popping into a very hot oven.