Monday, May 2, 2011

a chocolate cheat

I have mixed feelings about my microwave.

Oh, it has its uses. It's faster than an oven for reheating leftovers (and doesn't destroy risotto.) It's convenient for softening butter, which is nice if you're baking on short notice. And it's good for steamed vegetables on days when dinner could use the extra nutrients. Quite handy, really.

A microwave is an appliance with many applications. You can do fish en papillote in a microwave. You can roast garlic in a microwave. You can even make candy in a microwave. All the same, the spectre of frozen TV dinners lingers, and I can't help but feel that it's a bit like cheating. I've lived quite comfortably without a microwave in the past. It's not an essential kitchen appliance, is it?

Well, as it turns out, it does affect the picture when there's chocolate involved. You see, it's much, much easier to temper chocolate with a microwave than it is to do it with a chilled surface and a pan of simmering water on the stove.

Tempering is the process of melting chocolate in a way that allows it to harden and keep its shape when it cools.  You can't melt chocolate and expect it to harden to its original state on its own because chocolate is a curiosity: the fat crystals in cocoa butter form differently depending on the rate of cooling. Left to its own devices, the chocolate will cool with big crystals in a loose structure, and the end result will be dull in appearance and soft to the touch. (Consider the chocolate in chocolate chip cookies, and how they remain sticky even when the cookies have cooled.) If the cooling is controlled, however, the crystals formed are small and tightly arranged, and the chocolate becomes glossy and hard.

(You can read more about the chemistry of chocolate and tempering in this excellent article over at Cooking For Engineers.)

Tempering chocolate the old-fashioned way involves melting chocolate over simmering water, cooling some of it (typically on a marble slab or other chilled surface), and then reheating it just enough to bring it back up to the magical temperature point of thirty-one degrees Celsius, or eighty-eight degrees Fahrenheit. It requires the use of a chocolate thermometer, and I have yet to manage it successfully. (There's another, slightly less involved method known as "seeding": melting a small quantity of chocolate, and adding small "seeds" of unmelted chocolate to bring the temperature back down - but I've had no luck with that method either.)

With a microwave, however, you can take advantage of the flip side of chocolate's curious nature: its melting properties. Melted chocolate, you see, has stages. There’s the soft stage – what happens when you leave a chocolate bar out in the sun. There’s the gooey stage – what happens when you leave a chocolate bar near a heat source. And then there’s the liquid stage – what happens if you expose a chocolate bar to direct heat.

If you use good-quality chocolate (which is already tempered), and melt it in the microwave to a middle ground between soft and gooey, what you'll get is melted chocolate that is still tempered. The melted chocolate can be used to dip strawberries, coat caramels, or decorate biscotti, and it will harden as it cools, no extra steps required.

For the time being, I'm calling a truce on mixed feelings about my microwave. There's something to be said for not having to fuss with chilled marble and a chocolate thermometer, even if it does still feel a bit like cheating.

Chocolate Hazelnut Biscotti with Chocolate Drizzle

Caramelized white chocolate makes for the most arresting visual contrast, but milk or dark chocolate are also fine, flavor-wise. For a deeper flavor, add two teaspoons of instant coffee powder to the dough along with the cocoa powder.

(Makes twelve to fifteen, depending on how wide you slice them. Will keep in an airtight container for two to three weeks.)

Preheat oven to 325F. Line a baking sheet with parchment paper.

In a large mixing bowl, stir together a quarter-cup of olive oil, a quarter cup plus two tablespoons of sugar, a heaped quarter-teaspoon of salt, and a quarter-teaspoon of vanilla extract. Beat in two egg whites.

Stir in a quarter-cup of cocoa powder and one cup of all-purpose flour to form a stiff dough. Fold (or knead) in half a cup of chopped toasted hazelnuts.

Turn the dough out on the baking sheet. Shape into a log approximately twelve inches long; then flatten into a rectangle approximately four inches wide. Bake for twenty-five to thirty minutes, or until the surface has small cracks in it.

Remove from oven, and slide onto a cutting board. Use a serrated knife (or a sharp chef’s knife) to cut the biscotti on an angle into slices a little less than a half-inch thick. Arrange the slices, cut side up, on the baking sheet. Return to the oven, and bake for an additional twenty to twenty-five minutes, or until biscotti are mostly firm to the touch.

Cool the biscotti on a wire rack.

To decorate, begin by finely chopping or grating four ounces of the chocolate of your choice. Place in a small bowl, and microwave on low heat, twenty seconds at a time, until the chocolate starts to melt. Stir between each interval in the microwave. Stop heating once the mixture is mostly smooth, but still contains a few bits of solid chocolate. Stir until the last bits of solid chocolate melt. The mixture should be smooth but thick, and a little sticky.

Lay out a sheet of wax paper. Spread each piece of biscotti with chocolate on one side, then place it chocolate side down on the wax paper. If the chocolate starts to get difficult to spread, return it to the microwave (ten second intervals) until it softens.

Take a square of parchment paper and fashion it into a piping bag (or use a Ziploc bag.) Spoon the chocolate into the bag, and cut off the very tip. Drizzles or scribble designs all over the biscotti. Allow to set completely before peeling away from the wax paper.

Serve with tea or coffee.