1tablespoonfresh thymechopped, plus more for garnish
1tablespoonsalt
½tablespoonpepper
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Instructions
Preheat your oven to 350 degrees and spray an 8x8x3 baking dish with non-stick spray.
Peel and thinly slice the potatoes, ⅛ to ¼ of an inch thick. Soak in water until ready to use.
Then prepare the sauce, by melting the butter in a large skillet over medium heat. Add the onions and cook until softened and translucent, about 5 minutes. Then add the garlic and cook for 1 minute more.
Whisk in the flour until no lumps remain. Slowly whisk in the milk, followed by the chicken stock and bring to a boil. Whisk until the mixture thickens, then remove it from the heat and whisk in 1 cup of the cheese, the thyme and half of the salt and pepper.
Layer half of the potatoes into the prepared baking dish and season with ⅓ of the salt and pepper. Pour half of the cheese mixture on top of the potatoes in the baking dish. Layer with the remaining potatoes, season with the remaining salt and pepper and pour the remaining cheeee sauce on top. Then sprinkle the remaining ¼ cup of cheese on top.
Cover with foil and bake for 40 minutes, then remove the foil and bake an additional 10-15 minutes or until the cheese on the top becomes golden brown and bubbly.
If desired to serve as a thicker mixture, let casserole sit for 5-10 minutes before serving, otherwise the sauce will be loose and runny.
Notes
Soaking the potatoes in water before cooking them will remove excess starch, which prevents the potatoes from getting gummy. You can use a mandoline to thinly slice the potatoes, but be very careful. To make ahead: prepare and bake the casserole. Let cool completely before refrigerating overnight. Prior to reheating, let casserole sit on the counter for 20-30 minutes, then bake for 20-30 minutes at 350 (until heated through)