tempering chocolate... pepperoni?
For the cooking club last weekend I got to try a new (to me) cooking skill -- tempering chocolate. Chocolate is an interesting beast, as far as temperature goes. Let stored chocolate get too warm, and the cocoa butter melts and recrystalizes, forming that chalky-looking bloom on the surface. Get chocolate too hot and it burns. Melt it, then let it cool rapidly, and the result is greasy, soft, and unpleasant.
Harold McGee explains in the new version of On Food and Cooking:
Cocoa butter can solidify into six different kinds of fat crystals! Only two are stable kinds that produce a glossy, dry, hard chocolate; the other four are unstable kinds that produce a looser, less organized network, with more liquid fat, and crystals whose fat molecules readily detach and ooze away.
To temper chocolate, the chocolate is carefully melted, then reduced to about 90 degrees Farenheit, and stirred at that temperature while the right kind of crystallization happens. Adding some chopped chocolate to the mixture when it's about 95 degrees helps, as it adds "seed crystals" to the mixture and helps tempering occur faster. Cooking for Engineers has some good recommendations on how to temper chocolate relatively easily.
My excuse for learning this process was a pizza-themed dinner. I volunteered to do dessert, along with Jen, so for one of our dishes we made a strawberry chocolate dessert pizza. (The other dish was salted caramel ice cream, another dish that requires very careful control of temperature and crystallization, but I had nothing to do with it this time...) We made a cream cheese crust, cut into wedges, then spread strawberry jam over the crust, drizzled white chocolate sauce over the top, then topped with chocolate pepperoni and candied lime zest peppers. The full recipe is here, but I just want to talk about the chocolate pepperoni!
Learning how to temper chocolate was only half the battle! (And that half of the battle was not a cakewalk. One of the five times I tried to temper that weekend, it failed and I had to start over. Unfortunately, that was when I was under some time pressure...) The other half of the battle was figuring out how to make the tempered chocolate into perfect little discs.
For this, based on a suggestion from a pastry chef friend, I turned to power tools. I needed to make a plastic mold that would allow me to put the chocolate into that disk shape then let the chocolate harden. Initially, I used the lids from some takeout containers, but they turned out to be too thin. I then ransacked the apartment, looking for some thicker plastic, and ended up finding an old plastic photo frame I was going to throw away anyway. In a process that ended up spraying plastic dust all over the hallway, I then drilled 1/2" holes into the plastic with a spade bit, scraped the holes clean with a utility knife, then sanded everything relatively smooth with 600 grit sandpaper. The result looked like this, a small piece of hard plastic with nice circular holes in it, ready to be used for chocolate making.
Next was the chocolate. I melted it over hot water, let it cool to 95 degrees, stirred in some seed chocolate, then let it cool as I stirred some more to about 88 degrees. I then used a rubber spatula to spread the chocolate over the mold (taped to a piece of parchment paper), then scraped off the top some.
I then let the chocolate discs cool, carefully popped them out of the mold (about 80% survived that process!), then used them to assemble the final dessert.
The dessert was tasty, although if I made it again, I would have used less jam and about twice as much chocolate pepperoni. And if I had to make the plastic mold again, I'd use a larger piece of a slightly thicker hard plastic, so I could make more discs at once and more of them would survive, and I would have tried harder to make the walls of the holes beveled in one direction (like this: \ /, not this: > <), which would have helped them release better from the mold. Additional hardening time would have helped too, as the crystallization is a slow process, and fully tempered chocolate shrinks a few percent as it cools. All in all, though, it was a successful experiment!
And a preview of coming attractions and my next experiment... dairy-free truffles...