From Recipes from the Root Cellar by Andrea Chesman

3 T butter
1 T safflower or canola oil
1 onion, sliced
3 large sweet potatoes, peeled, halved if large and cut into 1 ince slices
1 T crushed dried rosemary
1 cup apple cider
salt and freshly ground black pepper
2 large apples, peeled, cored and cut into 1 inch wedges

Melt the butter in the oil in a Dutch oven over medium heat. Add the onion and sweet potatoes and saute until the onion is limp, about 3 minutes. Add the rosemary and cider. Season with salt and pepper. Bring to a simmer and cook for 15 minutes. Stir in the apples and cook until the potatoes are tender, 15 minutes longer. Serve hot.