Preheat your oven to 350°F (175°C).
Peel the potatoes and slice them very thinly (about ⅛ inch thick), using a mandoline if possible. Rinse and pat dry with paper towels.
Cut one garlic clove in half and rub the cut sides all over the inside of a 9x13 inch (23x33cm) baking dish. Butter the dish thoroughly.
In a medium saucepan, combine cream, milk, minced garlic, thyme sprigs, and bay leaf. Bring to a gentle simmer over medium-low heat.
Remove from heat and discard the herbs. Stir in salt, pepper, and nutmeg.
Arrange one-third of the potato slices in overlapping rows in the prepared dish. Pour one-third of the cream mixture over the potatoes.
Repeat with two more layers, finishing with cream mixture on top. Ensure liquid comes just below the top layer of potatoes.
Cover tightly with aluminum foil and bake for 45 minutes.
Remove the foil and continue baking for 30-40 minutes until golden brown on top and potatoes are tender when pierced with a knife.
Let rest for 15 minutes before serving.
