Preheat oven to 350°F. Wrap the bases of ice cream cones in foil. Stand each cone in a 2-1/2-inch muffin cup. If necessary, press additional foil into cups to secure cones.
Prepare batter for White Cake as directed. Spoon batter into ice cream cones, filling each half full. Bake for 20 to 25 minutes or until a wooden toothpick inserted in the centers comes out clean. Cool completely in muffin cups on wire racks.
Spoon whipped topping into a decorating bag fitted with a 1/2-inch round decorating tip. (Or fill a heavy resealable plastic bag with whipped topping; cut a 1/2-inch hole in one corner of the bag.) Pipe two mounds of whipped topping onto each cupcake cone to resemble scoops of ice cream. Freeze for at least 1 hour.
Place each color of candy coating in a microwave-safe bowl; add 1 teaspoon of the shortening to each bowl. Microwave, one bowl at a time, on 100 percent power (high) for 1 minute. Stir; microwave for 30 to 60 seconds more or until melted and smooth, stirring every 15 seconds. Set bowls in a pan half-filled with boiling water to prevent coating from thickening.
Remove cupcake cones from freezer. Dip the top of each cone into melted coating, letting excess coating drip off. (As you work, dip four of the cones into one color of coating, then dip the next four cones in another color, and so on.) Stand dipped cones on a sheet of waxed paper. While coating is still wet, sprinkle with jimmies. Let stand until coating is firm.
Twenty-four 2-1/2-inch muffin cups
1/2-inch round decorating tip
Preheat oven to 350°F. Allow butter and egg whites to stand at room temperature for 30 minutes. Meanwhile, grease and lightly flour two 9x1-1/2-inch or 8x1-1/2-inch round cake pans; set aside. In a medium bowl stir together flour, baking powder, and salt; set aside.
In a large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Gradually add granulated sugar, about 1/4 cup at a time, beating on medium speed until combined. Scrape sides of bowl; beat for 2 minutes more. Add egg whites, one at a time, beating well after each addition. Beat in vanilla. Alternately add flour mixture and milk to butter mixture, beating on low speed after each addition just until combined. Pour batter into the prepared cake pans, spreading evenly.
Bake for 20 to 25 minutes for 9-inch pans, 30 to 35 minutes for 8-inch pans, or until a wooden toothpick inserted near the centers comes out clean. Cool cake layers in pans on wire racks for 10 minutes. Remove layers from pans; cool completely on wire racks.