Cream sugars and butter. Add melted chocolate. Beat yolks, add water and vanilla and blend. Gradually add yolk mixture to chocolate mixture, beat until light and fluffy. Sift together flour, salt,and baking soda. Alternately add flour mixture and milk, blending well after each addition. Beat egg whites until stiff, but not dry, fold into batter. Turn into 2 greased and floured 23 cm round pans, or one greased and floured 13x9x2 inch pan. Bake layers or loaf in 180ºC about 30-35 minutes, or until cake springs back when touched lightly. Turn out on cooling rack.