3poundsYukon gold potatoes peeled and thinly sliced
1/2cupsalted butter1 stick
1/2cupshallotsthinly sliced from about 6 shallots
2clovesgarlicminced
1/4 cupall-purpose flour
3cupswhole milkroom temperature
1tablespoonfresh thyme
2teaspoonssea salt
1/2teaspoonground black pepper
8ouncesGruyére cheesefreshly grated
Instructions
Preheat the oven to 350° F. Grease a 9x13 or 3.6 quart casserole baking dish with butter.
Lay the sliced potatoes in the prepared baking dish. (See note #1)
In a saucepan, melt the butter. Add the sliced shallots and sauté until softened, about 5 minutes. Add the garlic and sauté for another 30 seconds.
Add the flour and stir to thoroughly combine. Continue stirring and cooking for 1 minute.
Slowly pour in the milk, whisking while you pour. Add the salt, pepper, and thyme. Simmer gently, stirring often, for 1 to 2 minutes until the sauce thickens a bit. Taste and adjust seasoning as needed.
Pour the sauce over the potatoes. Use two forks to help the sauce get down in between some of the potatoes. Don't worry about doing this to every potato though, the sauce will naturally fill gaps as it cooks.
Cover the pan with the lid or aluminum foil and bake for 1.5 hours.
Uncover the baking dish and add the grated gruyére cheese. Bake uncovered for another 30 minutes. Turn on the broiler and broil for 2 to 3 minutes or until the top is golden brown.
Allow the potatoes to rest for about 20 minutes before serving. (See note #2)
Notes
When slicing the potatoes, try to keep the slices together so that it is easier to lay place them in the baking dish. I like to remove the round end pieces and use them to fill gaps at the end.
It's important to leave the dish to rest for about 20 minutes before serving. This will allow the sauce to thicken. Also, these potatoes are hot(!) right out of the oven so it's worth the wait.