Can I use a non-springform 6-inch cake pan with shorter (i.e. 2-inch) sides? Yes-and-no. Yes, you can. I tested it several times. But the cake mushrooms over the top of the pan, meaning that while it hasn’t spilled over for me, it still could. But mostly what happens is that the edges of this muffin top become more dry and want to break off the cake, and you don’t get the same nice flaky-topped texture you see here.

Is bittersweet (72%-ish) or semisweet (60%-ish) better here? Both work. While I’m not a big fan of super-bitter chocolate cakes, since there’s less chocolate here than most flourless cakes, it can definitely handle more bitter chocolate without making a bitter cake.

Can I beat the egg whites by hand? You could! It’s definitely a big arm workout but I believe in you. (Not me, you.)

Can I double this? Absolutely. For a bigger cake for bigger celebrations, you can bake it in a 9-inch springform. It should take 35 to 40 minutes.

Source note: While it’s not where I started with this recipe [I took a flourless chocolate cake I liked, reduced the chocolate and separated the eggs, as I do here], this cake turns out to share a lower-chocolate, high-lift camaraderie with Richard Sax’s wonderful Chocolate Cloud Cake — consider this a hat tip of appreciation!