My earlier theory -- that the chocolate (from the cocoa powder in the batter) needed to be set in order to prevent the cratering that was occurring during the cooling process -- turned out to be right. Instead of leaving the chocolate cupcake to cool on its own devices, I cranked the temperature up from the recommended 325 (F) to allow the extra heat from the temperature increase to "set" the structure of the cupcake.
But it's conventional wisdom that chocolate burns really easily. According to Paula Figoni of How Baking Works, chocolate must be melted carefully as they contain a mix of proteins and carbohydrates that are easily overheated. This is why chocolate must be melted using a double-boiler -- even low, direct heat from a stove top is enough to turn the chocolate into a burned, thick, lumpy mess.
The vanilla cupcakes needed an increase of 50 (F) -- from 325 (F) to 375 (F) -- to bake properly at high-altitude. Because of chocolate's highly-flammable (is that the right word? easily burnable?) properties, I hypothesized that they would need less of a temperature increase. So I started out conservatively with my temperature adjustment and increased the recipe's temperature of 325 (F) by 10 degrees to 335 (F). This is what the cupcakes looked like when they cooled:
So I cranked it up by another 5 degrees from 335 (F) to 340 (F). This is what the cupcakes looked like when they cooled:
Hard to tell from the aerial shot, but they pretty much looked the same as the cupcakes baked at the previous temperature of 335 (F). That is, slightly sunken and cratered in. If you look closely, you can even see the same fingerprint in the bottom cupcake -- meaning that this batch failed the Hummingbird "spring back" test. However, the batch did perform marginally better at the 20-minute toothpick test. Instead of coming out with liquid batter, the toothpick came out with a chunk of moist cake:
I rolled up my sleeves and cranked the oven from 340 (F) to 345 (F). This is what the cupcakes looked like when they cooled:
So how did these taste?
Hm. Not perfect. A little too soft and moist. Hummingbird Bakery cupcakes have a substantial fluffy, non-sticky crumb, but these were missing it.
I decided to try cranking up the temperature one last time -- by this point, I was nearly out of batter. These are the final batch of cupcakes baked at 350 (F):
I'll take the deeper brown as a sign of chocolate cupcakes cooked to perfection. I remember that the vanilla cupcakes, when cooked at previous temperatures, were pale and had a bit of an undercooked look about them. I didn't realize that chocolate also had an undercooked color!
Score, ladies and gentlemen. Score. I will publish the fully-adapted, high-altitude friendly recipe in these next few posts.