In a large mixing bowl, combine the butter, brown sugar, molasses, eggs and gingerroot. Combine the flour, ground ginger, baking powder, cinnamon, baking soda, salt and cloves; add to the molasses mixture alternately with water, beating just until combined.
Pour into a greased 13-in. x 9-in. x 2-in. baking pan. Bake at 350 degrees F for 25-30 minutes or until a toothpick inserted near the center of cake comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.
In a medium saucepan, combine the cream, butter and corn syrup; bring to a simmer over medium heat. Remove from the heat. Stir in chocolate and vanilla until smooth. Let stand until cool but still pourable, about 20 minutes.
Place a baking sheet underneath the wire rack. Reserve 1/2 cup glaze. Pour remaining glaze over cake; spreading with spatula cover top and sides. Chill cake and reserved glaze until glaze is just firm enough to pipe, about 1 hour.
Pipe reserved glaze in a decorative pattern over cake. Cover and refrigerate. Remove from refrigerator 30 minutes before serving.