1preheat oven to 325 and grease and flour a bundt or tube pan or 2 large loaf pans (for loaf pans, preheat oven to 350).
2cream together butter and sugar. add sour cream and mix. sift together flour, baking soda and salt.
3alternately add flour mixture and eggs (beating well after each addition). add vanilla and beat to combine. pour into prepared pans.
4bake for 1 hour and 20 minutes for bundt or tube pan or 45 minutes for loaf pans or until toothpick inserted in center comes out clean. invert onto cooling racks and cool completely.
5whisk the cream into powdered sugar, then mix in vanilla and the seeds from the vanilla bean. (split the bean and scrape the seeds out).
6stir in additional cream as needed for desired consistency. drizzle over cooled cakes.