Preheat oven to 180ºC . Stir together flour and baking soda. In mixer bowl, beat sugar and butter until fluffy. Beat in eggs, one at a time, until smooth; add vanilla. Beat in sour cream alternately with flour mixture. Fold in chocolate chips. Pour into well-greased and floured 25 cm fluted tube cake pan. Bake 1 hr. and 15 min. or until wooden pick comes out clean. Cool; remove from pan. Sprinkle with confectioners' sugar if desired. Yield: 1 ten-inch cake