Course: Side Dish
Cuisine: American
Diet: Vegetarian
Key Ingredient: Gruyère, rosemary, sweet potatoes, thyme
To make ahead: prepare and bake through step 4, but stop cooking after 2 hours. Let chill, then cover, and keep in the fridge for up to 4 days. Before baking, bring the dish to room temperature, add the parmesan cheese and rosemary, and bake for another 20-30 minutes.