My mother began the tradition. Every 4th of July: BBQ, fireworks, and Flag Cake. This isn't the easiest cake you'll ever make, but it's worth it. I start making it a day ahead (I think you'll see why when you read the directions).
Flag Cake
1 box white cake mix
3 eggs (or number called for on boxes of cake mix)
Cooking oil (for cake mix)
Water (for cake mix)
1 box each 4 1/2 serving size red and blue jello (I prefer strawberry and berry blue)
2 cups boiling water
1 box, 4 serving size, instant vanilla pudding mix (fat free sugar free is just fine)
2 cups cold milk
1 8 oz tub cool whip (fat free is fine)
1 16 oz tub of cool whip (fat free is fine)
8 oz blueberries
1 pint strawberries
1 bag mini marshmallows
NOTE: I often do 2 separate white cakes instead of slicing one. This is entirely up to you. Of course that means having 2 boxes of cake mix and double the eggs, oil, and flour.
1. Prepare cake mix according to package directions. Bake in greased and floured 13 X 9 X 2 inch baking dish until knife inserted near center comes out clean. Allow to cool 10 minutes. Depan cake onto large baking sheet covered in aluminum foil (or whatever surface you plan to use to serve your cake from. Cover with aluminum foil or plastic wrap and chill at least 2 hours.
2. If you are using only one cake: Using large serrated knife slice cake horizontally through middle, making two equal layers. Take the end of a wooden spoon and poke holes in both cake layers about 1 inch apart. Do not poke all the way through (you'll want a smooth surface for frosting). First, prepare your red jello by mixing it with 1 cup of the boiling water for about 2 minutes, until fully dissolved. DO NOT ADD ANY COLD WATER. Use a turkey baster or spoon to pour the jello until each hole on one of the cake layers. Cover in foil or plastic wrap and place in refrigerator. Repeat with blue jello and second cake layer. Allow to chill at least 4 hours. BTW it doesn't matter which color goes on which layer ;). And I've gotten froggy some years and used BOTH colors by alternating them in the holes on the layers. Oooooh fancy I know :P.
3. Once the cake's chilled, make the filling: beat pudding mix and milk with wire whisk about 2 minutes, until pudding thickens. Allow to stand 5 minutes. Stir in 8 oz of cool whip and 1/2 cup each whole blueberries and diced strawberries (optional -- if your family's not wild about the fruit, leave it out). Spread on bottom cake layer. Top with second cake layer. Cover in foil or plastic wrap and allow to chill an additional 4 hours or more.
4. "Frost" cake with the 16 oz tub of cool whip (you might have some leftover -- that's fine. Use it to top your machiato while you finish decorating the cake). Now it's time to make this cake look like a flag! Create A "field of stars" in the upper left corner using whole blueberries. Thinly slice and halve stawberries and use them to create 7 "red stripes." Use the mini marshmallows to fill in your 6 "white stripes" OR skip the marshmallows all together and let the cool whip be your "white."
Serve cake immediately and refrigerate leftovers. If you're worried about the fruit browning, you can soak it in water and lemon juice for an hour before decorating the cake.