Ingredients
5 pounds Yukon gold potatoes
1 Large onion
8 tablespoon Butter
6 tablespoon Flour
1 teaspoon Dry mustard
1 cup Chicken broth
4 cup Whole milk
2 tablespoon Fresh thyme
4 Bay leaves
Preparation
Preheat oven to 400 degrees.
Place a saucepan over medium heat and add 2tbs butter. Saute onion until soft & translucent. Add garlic and thyme and saute for about 30 seconds, until fragrant. Remove mixture from pan. Using a whisk, swirl the 6tbs butter around in the pan until it’s almost melted. Add 6tbs flour and stir briskly to incorporate the flour and butter. Sprinkle in the mustard and salt and continue to cook for one minute over medium heat. Whisk in the chicken broth & milk and continue to stir, until the liquid comes to a rolling boil. Constantly stir and scrape the bottom of the pan while the sauce continues to cook and thicken, about 1 minute. Add bay leaves, salt and black pepper to taste. Add sliced potatoes and onion mixture and coat well. Bring to a simmer, until the potatoes are a little tender. Adjust to taste.
Spray a 9x13" baking dish with vegetable spray. Spoon the potatoes into the dish, layering them as flat as possible. At this point, you can hold the dish until ready to bake, even overnight in the refrigerator.
Bake until cream is bubbling around edges and top is golden brown, about 15 minutes. Cool 10 minutes before serving.
To Make Ahead: Once the scalloped potatoes have been transferred to the baking dish and pressed into an even layer in step 3, they can be wrapped in plastic wrap and refrigerated for up to 24 hours. When ready to bake, add the cheese, cover with foil, and bake in a 400-degree oven until the mixture is hot and bubbling, about 45 minutes. Remove the foil and cook until the cheddar begins to brown, about 30 minutes longer. Let cool for 10 minutes before serving.
