recipe for scalloped potatoes

Scalloped Potatoes Ingredients: 2 pounds potatoes (Yukon Gold or Russet), peeled and thinly sliced 2 tablespoons butter 1 small onion, finely chopped 2 cloves garlic, minced 2 tablespoons all-purpose flour 2 cups whole milk 1 cup heavy cream 1 teaspoon salt 1/2 teaspoon black pepper