I don't know the precise origin of the recipe, I can only speculate that it was written on a box of Jello back in the day, so it may very well be a Jello-brand recipe, but I don't have an original copy of it. It was a treat my grandmother fixed when I was a small child (late 70's) and in my kid mind, it seemed magical - red, white, and green; fruit and cake all in one slice.
We hung on to the transcribed recipe and tried it again this year. I can't believe how simple it is. It gets its name from the need to poke the baked cake layers with a fork or a butter knife before you pour dissolved jello over it. It gets absorbed into the nooks and crannies and when you refrigerate it and frost it with cool whip, it produces a speckled cake that's just about guaranteed to get devoured by the little people.
Surprisingly, now that I'm an adult and looking at the ingredients - it can be done low-fat and low-calorie as well, which is a double bonus. Substitute the usual egg with a can of diet soda when you prepare the cake batter, use low-sugar gelatin, and fat-free cool whip if you're interested in making it low-fat and lower-calorie.
The outside layer of the cake will look like an odd combination of jello and sponge, but when you slice into it, it will make sense.
Voila! A finished slice. It's ideal to let the entire cake cool a second time for several hours once frosted, as cool whip doesn't hold as strongly as regular sugar frosting, but the outer layer of jello also helps hold things together.
1 package of white cake (enough to make two 8" round pan layers), egg, oil or water (or substitute one can of diet soda for the wet ingredients)
1 small pkg. each of lime and raspberry Jello gelatin (can be any flavor or color you wish, but these produce the 'truest' red and green)
1 8oz. container of Cool Whip or similar whipped topping (aerosolized whip cream won't work)
2 8" round baking pans
1. Prepare boxed cake according to directions, or make your own according to your own recipe as long as the resulting batter color remains white for contrast with the jello colors. Most brands call for an egg or oil and water, though you can eliminate those ingredients and pour in a can of diet soda to the dry ingredients to make a low-fat cake (yes, this does work.)
2. Allow each cake to cool in the pan for at least 15 minutes. Then take a fork or the end of a butter knife and "poke" the surface of the cooled cake layers - gently. There's not a need to poke directly through to the bottom, as the jello absorption process will take care of the bottom of the cake. This can be done in as little or as much of a space as you wish. The poke marks should be small, however, for best results.
3. Prepare the gelatin according to package directions for the boiling water only. This is important - there's no need to add the cold and/or additional water to the gelatin powder once you've dissolved it in the hot water. Adding the extra water could result in less firmness, the flavor won't be any different.
As an example, my pictured version was prepared with a large-size box of each flavor, which called for 2 cups of boiling water to dissolve, then two additional cups of cold water, if I were preparing the jello as jello. I dissolved the water in two cups of boiling water only. I had lots of leftover jello liquid that I didn't need.
4. With a large spoon, pour the warm jello liquid over the top of the cake, coating it evenly until you've nearly run out of jello. It will absorb into the cake. You know you've reached the saturation point when you can no longer see the gold color of the top of the cake. Don't be afraid of seeing the jello congregate on the sides, this is how it works, and you'll be surprised at how much liquid it will take to absorb through the "pokes" once the cake is done. Be generous with your pours!
5. Keep the layers in their original pans and return to the refrigerator to cool for a minimum of 3-4 hours until the jello is firm (hence why it's prepared with less water than the label instructions.) Loosen the sides with a butter knife or dip the pan in hot water for 10 seconds to loosen the jello.
6. Carefully, carefully, carefully turn the pan over to remove the finished cake and place on the frosting platter, one layer at a time. With the 8 oz. of Cool Whip cover the bottom layer, then add the top cake layer and use remaining Cool Whip to cover in its entirety.
For best results, return the finished cake to the refrigerator under a cake pan to let the cool whip firm up before slicing. Keep in mind that it will be slightly more fragile than a cake made with sugar frosting, so gentle hands and a good knife will be necessary if you're the type who's concerned about a clean finish.
Continue to store un-served portions in the refrigerator and enjoy your "magical" poke cake!