- 2 pounds yukon gold potatoes (6-7 potatoes), peeled and thinly sliced
- 1 large white sweet onion, peeled and thinly sliced
- 2 cloves garlic, minced
- 1 cup heavy cream
- 1 cup whole milk
- 1/2 cup gruyere or cheddar cheese, grated
- 3 tablespoons unsalted butter
- 3 tablespoons all-purpose flour
- 1 tablespoon fresh rosemary, minced
- 1/2 tablespoon fresh thyme, minced
- 1/4 teaspoon ground nutmeg
- kosher salt and freshly ground pepper, to taste
- Preheat oven to 400º F.
- Make an overlapping layer of 1/2 of potato slices along the bottom of a 9×13-inch baking dish, then top with 1/2 of onions and garlic.
- Season generously salt and pepper, then repeat layers with remaining potatoes, onion and garlic.
- Heat butter in a large saucepan over medium heat. Stir in flour and cook, whisking continuously, until smooth and paste-like. About 2 minutes.
- Slowly stir in milk and heavy cream and cook for 5-10 minutes, or until thickened, then mix in 1/2 of gruyere and stir until melted and smooth.
- Add nutmeg and season with salt and pepper, then taste and adjust seasoning, if necessary.
- Pour sauce evenly over potatoes and onions and top with rosemary, thyme and remaining cheese.
- Place baking dish in oven and bake for 1 hour, or until potatoes are fork tender and surface is golden brown. (Cover with aluminum foil if cheese is melting and browning too quickly.)
- Remove from oven and serve hot.
Source : allrecipes.com