Name: Potatoes Au Gratin
Prep time: 20 min
Cook time: 63 min
Total time: 83 min
Yield: 12
Ingredients: 3 pounds (approximately 8-10 medium) russet potatoes, rinsed, peeled, and thinly sliced with a mandoline; 6 tablespoons unsalted butter; ½ yellow onion, diced; ½ cup all-purpose flour; 2 teaspoons kosher salt; ½ teaspoon pepper; 3 cups whole milk, room temperature; 2 cups sharp cheddar cheese, shredded and divided; parsley, for garnish