Thomas Keller's recipe uses a quarter sheet pan, I used a 9" round cake pan. If you use the 9" round cake pan, increase the cooking time by 10-15 minutes.
I floured my pan and then used parchment paper in the bottom instead of using cooking spray. It works just as great!
To make sweetened whipped cream, whip about ¾ a pint of heavy whipping cream in your stand mixer fitted with a whisk. Add about 3 tbsp of confectioners sugar, this may fluctuate depending on your desired sweetness. Add a little sugar at a time and taste. Whisk on high for about two minutes until desired firmness. Don't over whip!
Also, I HIGHLY recommend using grams to measure your ingredients. When I started using a scale, my baking skills elevated immensely. Using a scale makes you a more consistent baker and it ensures your batter is the perfect chemical mix. Baking is science, after all!