Prepare cake pans by lining with parchment paper, greasing and lightly flouring.
Mix the cake mix following the directions on the box.
Divide the cake batter into two bowls.
Color one bowl of batter yellow and the other pink with the gel food coloring.
Pour the cake batter in the two prepared pans.
Bake the cake following the directions on the box.
Cool the cake completely on a wire cooling rack. Set aside.
Dissolve both boxes of blue JELLO in 2 ½ cups of boiling water and cool.
Poke holes all over the top of both cakes. (SEE NOTES)
Carefully pour the JELLO into each hole on both cakes. Cover the cake pans with plastic wrap.
Chill 4 hours at least or overnight.
Remove the first layer of cake from the pan and peel off the parchment paper. Place cake on a plate or cake stand.
Make the frosting
Scoop the vanilla frosting into a bowl.
Whisk one cup of cool whip into the frosting until combined.
Frost the cake
Spread some of the cool whip frosting over the top of the bottom layer of the cake to frost most of the center of the cake.
Remove the parchment paper and place the second layer of the cake on top of the bottom cake layer. (SEE Step 8 and 9 above in the post for detailed instructions)
Frost the sides of the entire cake.
Use remaining frosting to frost the top of the cake.
Chill before serving.
Makes 12 servings.
Recipe Expert Tips
Why use parchment paper? In my experience parchment paper is required to help keep the JELLO from leaking out the bottom of the cake layers.
What size cake pans: I used eight inch round cake pans. If you use nine inch round pans the cake layers will be thinner.
What brand cake mix to use?: Use your favorite white cake mix.
How to get the right JELLO colors: I made a yellow cake layer and a pink cake layer. By using blue JELLO the colors of the JELLO naturally combine and changed to green (yellow cake layer) and purple (pink cake layer) when poured into the holes poked into the cake.
How to poke the holes in a poke cake: I find the handle of a wooden spoon to be too wide that is why I use a chopstick. The smaller hole created by a chopstick helps the cake absorb the liquid JELLO as you pour it into each hole. If you don't have a chopstick try to find something smaller than a wooden spoon handle to use.