1. 3/4 teaspoon salt
2. 1/2 teaspoon ground black pepper
3. 1/2 teaspoon thyme
4. 2 tablespoons butter
5. 1 thinly chopped sweet onion
6. 1 1/2 pounds/700 grams Yukon gold potatoes, peeled and thinly sliced
7. 1 cup crushed Gruyere cheese
Prep:20 Minutes, Cook:43 Minutes, Ready In:1 Hours 8 Minutes
1. mix salt, pepper, and thyme in a bowl.
2. melt 1 tablespoon butter in a pan. cook onions till soft and golden brown,for 8 minutes. flow to a bowl.
3. melt 1 tablespoon butter in a pan; put off from heat.
4. set up 1/3 of potato slices within the pan in a barely overlapping layer. sprinkle with 1/2 teaspoon of the salt mixture. top with half of of the onions and half of of the gruyere cheese. repeat layers, ending with potatoes; sprinkle with final salt mixture.
5. cowl and cook over medium-low heat till potatoes are gentle,for 30 minutes. uncover and keep cooking,for 5 mins. run a spatula around edges to loosen;let it cool for 10 minutes.