Directions

• Preheat oven to 400° F. Grease the bottom and sides of a 9×13 inch casserole dish with a little butter, or nonstick spray. Set aside.
• Melt 1/4 cup butter over medium heat in a large pot. Thinly slice 1 onion and add to the butter. Sauté for 4-6 minutes until the onion is translucent.
• While it’s cooking, add 1 tablespoon kosher salt, 1/4 teaspoon black pepper, 1/4 teaspoon cayenne pepper, and 1/4 teaspoon dried thyme.
• After sautéing for 4-6 minutes, add 5 cloves of smashed and minced garlic. Cook for about 30 seconds.
• Sprinkle in 6 tablespoons of flour, adding about a tablespoon at a time and stirring in between. Cook mixture for about 30 seconds.
• Slowly whisk in 4 cups of cream. Once all of the cream is added, stir in 1/2 cup parmesan cheese, sprinkling it in a little at a time so that it melts nicely.
• Slice potatoes thinly into 1/8 inch rounds. Place them in a large bowl of water to prevent browning. Drain well.
• Add potatoes to the pot of sauce with the heat set to medium. Use a rubber spatula to stir the potatoes into the sauce, separating any slices that stick together to make sure they are all coated in sauce. Let the mixture come to a low bowl over medium heat, then reduce heat to medium low and cook for 10 minutes, stirring occasionally. After the cream and potato mixture has bubbled for about 10 minutes, turn off the heat.
• Pour half of the mixture into the greased 9×13 inch pan. Sprinkle the first layer with 1 1/2 cups sharp cheddar cheese.
• Top the cheese with the rest of the potato and cream mixture and spread to the edges. Sprinkle the top with 1 1/2 cups cheddar cheese.
• Bake at 400° for about 40 minutes.
• Let stand for 10 minutes before serving.