Some ice cream sandwiches use hard cookies, so when you take a bite, the ice cream has a tendency to squeeze out the other end. This ice cream sandwich has moist chocolate cake that sticks to your fingers, and you can make the ice cream without an ice cream machine.
For the chocolate sandwich cake: Preheat oven to 325 degrees F. In a stand mixer, cream the butter until soft. Meanwhile, in a separate bowl, thoroughly combine flour, baking soda, baking powder, and salt. When the butter is soft, add the sugar to the mixer and continue mixing to combine; add the cocoa in several batches, then the eggs one at a time.
Slowly add your dry ingredients to the cocoa mixture, alternating with the hot water to prevent lumps. When the ingredients have been incorporated and the batter is smooth, spread the batter onto a rimmed baking sheet prepared with no-stick spray and parchment paper. Bake for 15 minutes until tester comes out clean.
For the frozen vanilla custard: Prepare an ice bath to cool down the custard. Set aside. Gently bring the cream to a low boil in a medium saucepan over medium heat. Meanwhile, in a bowl, whisk sugar and egg yolks. Add the vanilla extract to the cream. When the cream is simmering, whisk the gelatin in until it dissolves. Pour a little sugar/yolk mixture into the cream, and continue whisking to combine. Then add the remaining sugar/yolk mixture and cook a little longer, but do not bring to a boil. When mixture starts to stick to the bottom, it's ready.
Strain the custard mixture into a bowl set in the ice bath. When the custard is at room temperature (about 5 minutes), fold in the whipped cream. Spread onto a ¼ sheet pan prepared with non-stick spray. Freeze at least 2 hours.
When the cake is out of the oven, run a knife around the edge, then invert onto another rimmed baking sheet lined with parchment paper. Remove the parchment paper from the top and cool completely. To assemble the custard sandwich: Cut cake into squares approximately 3x3-inches, then cut horizontally, making two chocolate sandwich cakes for each square. Cut the frozen custard into the same size squares and sandwich between the chocolate cake.
Please defer to the written recipe for measurements, as they've been adjusted from the video.