Dreamy Slow Cooker Scalloped Potatoes No Peel So Easy

Ingredients

• 2 1/2 lbs Yukon Gold potatoes, thinly sliced
• 1 medium yellow onion, thinly sliced
• 2 cloves garlic, minced
• 4 tablespoons unsalted butter, melted
• 3 tablespoons all-purpose flour
• 2 cups whole milk
• 1 cup heavy cream
• 1 cup shredded Gruyère cheese, plus more for topping (optional)
• 1/2 teaspoon ground nutmeg
• 1 teaspoon salt, or to taste
• 1/2 teaspoon black pepper, or to taste
• 2 tablespoons chopped fresh parsley, for garnish (optional)
• Cooking spray