Kale and Sweet Potato Gratin

Name: Kale and Sweet Potato Gratin
Ingredients: 5 tbsp. butter; 3 cloves garlic; Kosher salt and freshly ground black pepper, to taste; 1 bunch kale, stemmed and roughly chopped; 3 large sweet potatoes (about 2 1/2 pounds) peeled and sliced about 1/8″ thick; 2 cups half-and-half; 2 tsp. ground cinnamon; Fresh nutmeg; 1 cup grated white cheddar