Peel the potatoes carefully and slice them very thin using a sharp knife or mandoline slicer. Thin slices cook evenly and absorb the creamy sauce better. Try keeping the slices similar in thickness for smooth layered texture after baking.

In a saucepan, combine heavy cream, milk, minced garlic, salt, pepper and nutmeg. Heat gently over medium-low heat while stirring occasionally. The warm cream mixture helps infuse garlic flavor throughout the potatoes while creating rich creamy sauce for baking.

Rub butter around the inside of the baking dish carefully. This prevents sticking and adds extra richness. A well-buttered dish also helps create beautiful golden edges around the creamy potato layers during baking inside the hot oven.

Arrange a layer of sliced potatoes across the bottom of the dish evenly. Slightly overlap the slices for better texture. Continue layering carefully while sprinkling small amounts of Gruyère cheese between some layers for rich savory flavor throughout.

Slowly pour the warm cream mixture evenly over the layered potatoes. The liquid should cover most of the slices without overflowing. This creamy mixture softens the potatoes beautifully while baking and creates the signature rich dauphinoise texture.

Sprinkle the remaining Gruyère cheese generously across the top layer. The cheese melts beautifully while baking and forms golden crispy topping. This step adds rich savory flavor and creates the classic bubbling cheesy surface everyone loves.

Cover the baking dish loosely with aluminum foil and place into a preheated 350°F or 175°C oven. Bake for about 45 minutes. Covering first helps the potatoes soften gently without the top becoming overly brown too early.

Carefully remove the foil after 45 minutes. Return the dish to the oven and bake another 20 to 25 minutes until golden brown. The potatoes should feel tender when pierced with a knife while the top looks bubbling and crispy.

Remove the dauphinoise from the oven and let it rest for about 10 minutes before serving. Resting helps the creamy sauce thicken slightly. Garnish with fresh thyme if desired and serve warm beside your favorite main dishes.