1. Peel, dice, and cook potatoes; mash with 1 tablespoon margarine and milk.
2. Preheat oven to 400° F.
3. Put potatoes in 2-quart baking dish, forming a nest in center. Bake for 20 minutes or until lightly browned.
4. While potato is in oven, cook rutabaga until tender. Drain. Season with salt, pepper, and remaining 1 tablespoon margarine.
5. Spoon into potato nest.
6. Sprinkle with chopped parsley.