Side Dish - Mashed Potato Rutabaga And Parsnip Casserole With Caramelized Onions

Rutabagas and parsnips add an earthy sweetness to mashed potatoes that are then topped with caramelized onions and baked. This dish is great for entertaining, as it can be made a day ahead; just bake until it's heated through and the top begins to crisp.