Mash yams well. Add butter, eggs, salt, cinnamon, brown sugar and cream or juice if needed. Spoon into well greased baking dish. Combine flour, brown sugar, cinnamon and salt. Cut butter into mixture until it resembles coarse crumbs.
Press marshmallows lightly into top.
Bake at 350 degrees for 25 minutes. Mix together dry ingredients. Cut in margarine until mixture resembles coarse crumbs. Toss 1 cup crumb mixture with yams and cranberries. Top with remaining crumbs.