Chocolate and Vanilla Swirl Cake

Preheat oven to 350 degrees.  Mix together flours, salt, baking soda and baking powder.  Set aside.

Beat butter, granulated sugar and vanilla until fluffy.  Add eggs one at a time, beating well after each addition.  Beat in flour mixture, alternately with yogurt, beating until smooth after each addition.

Remove 1 cup of batter.  Stir in cocoa mix.  

Pour half of the plain batter into a greased and floured 9-by-5-inch loaf pan.  Drop cocoa batter by spoonfuls onto plain batter in pan.  Add remaining plain batter.  Swirl batters deeply with handle of wooden spoon for marbled design.

Bake 1 hour to 1 hour 15 minutes or until toothpick inserted in the center comes out clean.  Cool 10 minutes.  Loosen sides of cake from pan.  Remove from pan to wire rack.  Cool completely.

To serve, stir together powdered sugar and milk.  Drizzle over cake.  Slice.