Ingredients
Equipment
Method
Prep and heat the oven
- Preheat the oven to 375F, then butter a 9x13-inch baking dish for easy release and browning.
Make the creamy sauce
- Melt the butter, then cook the garlic for 30 seconds until fragrant.
- Whisk in the all-purpose flour and cook for 1 minute to remove the raw flour taste.
- Gradually whisk in the whole milk and heavy cream, then simmer until slightly thickened.
- Season the sauce with salt, black pepper, and fresh thyme leaves, stirring so the herbs disperse.
Layer and bake
- Layer the sliced potatoes and onion in the dish in three layers, then pour sauce over each layer so everything is moistened.
- Cover with foil and bake for 1 hour at 375F to cook the potatoes through.
- Uncover, sprinkle with Parmesan, and bake 25-30 minutes at 375F until the top is golden and a fork slides through easily.
Rest and serve
- Rest the scalloped potatoes for 15 minutes before serving so the sauce thickens and layers set.
Notes
For the neatest layers and even cooking, slice the potatoes to about 1/8 inch and keep them submerged in cool water only if you need to pause before layering. Refrigerate leftovers in a covered container for up to 4 days; reheat in a 325F oven until hot throughout. Freezing is not recommended because the cream sauce can separate after thawing. For a lighter option, use half-and-half instead of heavy cream (sauce will be slightly less thick).
