Vegetable oil spray
3 pounds russet potatoes (about 6 medium), peeled and sliced ¼ inch thick
1¼ cups heavy cream
1 tablespoon unsalted butter
4 garlic cloves, minced
2 teaspoons minced fresh thyme, or ½ teaspoon dried
1¼ cups low-sodium chicken broth
4½ tablespoons cornstarch
¼ teaspoon salt
½ teaspoon pepper
¾ cup shredded sharp cheddar cheese (3 ounces)
¾ cup shredded Monterey Jack cheese (3 ounces)
1. Line slow cooker with aluminum foil collar and coat with vegetable oil spray. Microwave potatoes with 2 tablespoons cream in covered bowl, stirring occasionally, until nearly tender, 6 to 8 minutes; let cool slightly.
2. Melt butter in medium saucepan over medium heat. Add garlic and thyme and cook until fragrant, about 30 seconds. Whisk broth, remaining cream, cornstarch, salt, and pepper together, then whisk into saucepan. Bring to simmer, whisking constantly, and simmer until thickened, about 1 minute. Slowly whisk in cheddar and Monterey jack until completely melted.
3. Spread half of sauce over bottom of prepared slow cooker. Shingle potatoes over sauce, then spread remaining sauce evenly over potatoes. Cover and cook until potatoes are tender, 4 to 6 hours on low.
4. Remove foil collar and let potatoes cool for 20 minutes before serving. (This dish does not hold well on warm setting.)