Preheat oven to 350°F and line a 9x13-inch pan with parchment paper or spray with non-stick cooking spray.
In a large bowl with an electric hand mixer, beat together the cake mix, water, oil and eggs or egg whites on medium-high speed for 2 minutes. Be sure to scrape the bottom of your bowl as needed.
Use a rubber spatula to gently fold in the chopped freeze-dried strawberries into the batter.
Pour batter into the prepared pan and use an offset spatula or spoon to spread the batter into an even layer.
Bake in preheated oven for 30-35 minutes, or until the top of the cake springs back when lightly touched.
Allow cake to cool for 20 minutes. Using a smoothie straw or the handle of a wooden spoon, poke holes across the cake, spaced every inch or so, halfway into the cake.
In a large liquid measuring cup with a spout, whisk together the strawberry jello mix and boiling water until the gelatin is fully dissolved. Carefully pour strawberry gelatin evenly over top of cake. Cool completely on a wire rack.
Evenly spread the whipped topping onto the cake. Cover and refrigerate for at least 4 hours.
Just before serving, top with sliced strawberries.
Notes
Different brands of white cake mix often require different amounts of water, vegetable oil, and eggs or egg whites. Refer to the box of the brand you purchased for the correct amounts you will need.Most brands of white cake mix are 15.25 ounces. Betty Crocker white cake mixes are 16.25 ounces – if you use a Betty Crocker mix, make sure to refer to the box for the correct amount of ingredients needed to make the cake batter.If using only egg whites in this cake, do not discard the egg yolks – save them for another use, such as making lemon curd or lime curd.