A rich cake, this improves with keeping in an airtight tin. Very nice served with tea. Preheat oven to 325F (165C). Generously grease an 8-inch square baking pan; set aside. Sift flour, salt, baking soda and ground ginger into a large bowl. Stir in raisins (plump then in some sherry or water before using), candied peel and cystallized ginger; set aside. In a medium-size saucepan, combine molasses, butter and brown sugar. Stir over low heat until butter is melted. Remove from heat. Beat in eggs and milk. Make a well in center of reserved dry ingredients. Pour in molasses mixture and beat thoroughly. Pour into cake pan. Bake 1 1/4 hours, or until top springs back when lightly touched with finger. Cool in pan on a wire rack. Makes 8 to 12 servings.