Preheat oven to 325F/160C. Spray a 10-cup tube pan with non-stick spray.

In a saucepan, melt chocolate with water over low heat. Mixture will begin to harden.

In a large bowl, cream butter and sugar until light and fluffy, 5-7 minutes. Add eggs, 1 at a time, beating well after each addition.

Beat in vanilla and the chocolate mixture. Combine the flour, salt and soda; add to creamed mixture alternately with buttermilk.

Pour into prepared pan. Bake for 1-1/2 hours or until a toothpick inserted in the center comes out clean. Let stand for 10 minutes before removing from pan to a wire rack to cool. Sprinkle with confectioners' sugar if desired.