Preheat the oven to 325 degrees F and line a cookie sheet with parchment paper.
In the bowl of a stand mixer fitted with the whisk attachment, combine the eggs, sugar and salt. Beat on high until light and tripled in volume, about 5 minutes. Add the vanilla and beat again. Add the flour and baking powder and fold to combine with a rubber spatula.
Transfer the batter to the prepared pan and smooth it out with a small offset spatula, until it practically covers the paper lining. Bake until golden and crisp about 25 minutes (I found this took longer than the time (15 minutes) that Shauna allotted).
Let cool to room temperature while you cut the marshmallows into quarters with a kitchen scissors. Tedious, as Shauna tells us, but worth it.
Clean the stand mixer bowl and whisk attachment, and whisk the cream until stiff peaks form. Crumble the cookie and fold in to the whipped cream, along with the chopped up marshies. Cover the bowl with plastic wrap and place in the refrigerator for 2 hours. Serve with a dusting of cocoa powder and some slices of strawberries.