Crockpot Scalloped Potatoes

Steps

1. 1Make the Sauce
2. 2Soften onion
3. 3Melt 4 tablespoons butter in a large skillet over medium heat. Add 1 large yellow onion, finely diced, and cook until very soft and lightly golden, about 6–8 minutes.
4. 4Add garlic
5. 5Stir in 3 cloves minced garlic and cook for 30 seconds.
6. 6Thicken with flour
7. 7Sprinkle in ⅓ cup all-purpose flour and cook, stirring constantly, for 1–2 minutes to remove the raw flour taste.
8. 8Add liqids
9. 9Slowly whisk in 2 cups whole milk, 1 cup chicken broth, and ½ cup heavy cream. Bring to a gentle simmer and cook until thickened, about 3–5 minutes.
10. 10Season
11. 11Stir in 1½ teaspoons kosher salt, ¾ teaspoon black pepper, ½ teaspoon smoked paprika, and ½ teaspoon Dijon mustard. Taste and adjust seasoning.
12. 12Layer the Potatoes
13. 13Layer potatoes with sauce
14. 14Lightly butter slow cooker insert. Layer one-third of 3 pounds peeled, sliced Yukon gold potatoes in an even layer across the bottom.
15. 15Spoon one-third of sauce over potatoes, then sprinkle with one-third of 1 cup shredded cheddar or gruyere and one-third of ¼ cup grated parmesan.
16. 16Repeat layers two more times with remaining potatoes, sauce, and cheese, finishing with remaining sauce and remaining parmesan on top.
17. 17Cook in Crockpot
18. 18Add paper towels and cook
19. 19Place a double layer of paper towels across the top of slow cooker insert, then cover with lid. Cook on LOW for 5–6 hours or on HIGH for 2½–3 hours, until potatoes are very tender when pierced with a knife.
20. 20Rest
21. 21Remove lid and let rest uncovered for 15 minutes before serving to allow sauce to thicken.
22. 22Optional Finish
23. 23Brown top
24. 24For a golden, browned top: transfer to a baking dish, sprinkle extra cheese over top, and broil for 3–5 minutes until golden and bubbling.