1. Cream butter; gradually add sugar and beat 10 to 15 minutes at medium speed of electric mixer. Add eggs one at a time, beating well after each addition.
2. Combine flour, baking powder, soda and salt;.
3. add to cream mixture alternately with buttermilk and oil, beginning and ending with flour mixture.
4. Mix well after each addition.
5. Stir in flavoring.
6. Pour batter into three greased and floured 9-inch round cake pans.
7. Bake at 350°F for 20 to 25 minutes, or until a wooden toothpick inserted in the center comes out clean.
8. Cool cake in pan for 10 minutes.
9. Place on wire rack and let cool completely.
10. Combine milk and flour in medium saucepan.
11. Cook over medium heat, stirring constantly until mixture thickens.
12. Remove saucepan from the heat, and allow mixture to cool completely.