Cook sweet potatoes until tender. Drain, cool, peel, and cut in half lengthwise (canned sweet potatoes may be substituted). Arrange in greased shallow baking dish.
Mix salt, brown sugar and flour together. Sprinkle over potatoes. Dot with butter. Add marshmallows and nuts and pour half and half or evaporated milk over all. Bake at 350 degrees for 45 to 50 minutes.