3 pounds Russet or Yukon Gold potatoes, peeled and sliced into 1/8 inch rounds
1 small yellow onion, very thinly sliced
3 cloves garlic, minced
4 tablespoons butter
1/4 cup all-purpose flour
2 cups whole milk
1/2 cup heavy cream
2 cups sharp cheddar cheese, shredded
1 teaspoon salt
1/2 teaspoon black pepper
1/2 teaspoon dried thyme or rosemary
Fresh parsley for garnish
Instructions
Start by peeling your potatoes and slicing them into thin, even rounds about an eighth of an inch thick. If you have a mandoline slicer, this is the perfect time to use it to ensure even cooking. Grease the inside of your slow cooker with a little bit of butter or non-stick spray to prevent sticking during the long cook time.
In a medium saucepan over medium heat, melt the butter. Stir in the minced garlic and cook for about one minute until fragrant. Whisk in the flour and cook for another minute to remove the raw flour taste. Slowly pour in the milk and heavy cream, whisking constantly to prevent lumps. Continue to cook and stir until the sauce thickens enough to coat the back of a spoon. Remove from heat and stir in salt, pepper, and herbs.
Place half of the sliced potatoes and half of the sliced onions into the bottom of the prepared slow cooker. Sprinkle with one cup of the shredded cheddar cheese. Pour half of the prepared white sauce over the layer. Repeat with the remaining potatoes, onions, and sauce, but hold back the remaining cup of cheese for the final stage of cooking.
Cover the crockpot with the lid and cook on High for 4 to 5 hours or on Low for 7 to 8 hours. You will know they are ready when the potatoes are fork-tender and the sauce is bubbling. Avoid opening the lid too often during the process as this releases the heat and extends the cooking time.
About 20 minutes before serving, sprinkle the remaining cup of cheddar cheese over the top of the potatoes. Cover the lid again and let it melt until it is gooey and golden. Garnish with fresh parsley before bringing the pot to the Christmas table.
