Preheat oven to 400 degrees. Place a piece of parchment paper in a 15x10 x1 inch pan. Spray the parchment paper with nonstick cooking spray and then dust with cocoa powder.
In a medium bowl, add the eggs and sugar. With a hand mixer, beat on medium until the eggs are pale and fluffy.
In a separate bowl, sift the flour, cocoa powder, and baking powder.
Fold a third of the flour into the egg mixture.
Once all the flour is folding in, add another third of flour. Continue folding. Repeat with the last bit of flour.
Pour into the prepared jelly roll pan. Smooth the batter out so it reaches all the sides and corners. Give it a tap on the counter.
Place in the oven for 5 to 7 minutes. Remove from the oven and let sit for a minute or two.
Start rolling the warm cake the long ways while it's still on the parchment paper. This will shape the cake and you won't get splits in the cake as you roll it back up after you fill it. The parchment paper will prevent the cake from sticking together when it's rolled up. Let it cool all rolled up.
Buttercream
In a metal mixing bowl, over a double boiler, add in the sugar and egg whites. The water should be at a steam or gentle boil. Also, make sure the hot water doesn't touch the bottom of the mixing bowl. It will cook the egg whites.
Whisk the sugar and egg whites together to help dissolve the sugar. You want to use a candy thermometer and let the egg mixture come up to about 115 degrees. The eggs will be smooth and shiny.
Remove the mixing bowl from the double boiler. Using a stand mixer and whisk attachment, turn the mixer on low to help cool down the egg whites. Turn the mixer up on medium high until it reaches stiff peaks. It'll probably take about 5 minutes.
Once the meringue is at stiff peaks, add in vanilla and 2-3 tablespoons of butter at a time. Let it incorporate and then add in a few more pieces. My buttercream wasn't firming up, so I placed it in the freezer for about 8-10 minutes. I mixed it after I took it out of the freezer and it whipped right up like a swiss meringue buttercream.
Cookie Dough
In the stand mixer, add in the butter. Let it mix for 30 seconds.
Add in the brown sugar and granulated sugar. Mix until the mixture becomes light and fluffy.
Add in the softened ice cream and mix until completely incorporated.
Add in the heaping cup of flour and mix until combined. The mixture will be kind of thin.
Add the swiss meringue buttercream into the cookie dough and mix.
Voila. Cookie Dough Swiss Meringue Buttercream.
Assemble
Unroll the cake and smooth buttercream on the cake. Make sure you get the curl that will be in the center of the cake. You will have extra buttercream. You can freeze it or use it in another recipe.
Roll the cake up and cut the ends of the cake. Make a cut in the middle to have two rolls.
Roll up in plastic wrap and refrigerate.
Notes
The cake recipe was adapted from Hershey and the buttercream recipe was adapted from The Baking Cup.