Sponge Cake Guru

Finally, I think I've mastered the sponge cake. They've always collapsed in previous attempts.

What worked:
- Beating egg whites even stiffer than I thought they should be
- Folding in egg whites a portion at a time
- Tipping springform pan upside down while cooling
- Using cake flour (1 cup + 2 Tbsp = 1 cup all purpose)

Otherwise essentially followed this Tres Leches recipe