Combine first six ingredients in bowl; add milk, shortening and vanilla. Using an electric mixer, beat on low speed until combined, then beat on medium for 2 minutes. Add egg and beat two more minutes.
Pour into buttered and floured 9-inch baking pan. Bake 25 to 30 minutes (or until toothpick inserted near center comes out clean). Cool on rack for 10 minutes. Remove from pan and cool thoroughly on rack. YIELD 8 servings.