This recipe is best with the pale gold sweet potatoes that are frequently labeled “yams.” They are a little less sweet and much drier and starchier than the dark orange ones. These soufflés are not the delicate little darlings you may have feared. They can even be made in advance and frozen, and they’ll still puff up.
6 SERVINGS
1 |
medium to large sweet potato (see headnote) |
3 |
tablespoons ricotta |
2 |
large egg yolks |
¾ |
teaspoon salt |
3 |
slices prosciutto |
5 |
large egg whites |
⅛ |
teaspoon cream of tartar |
Heat the oven to 375 degrees. Put the sweet potato on a baking sheet and bake until it is easily pierced to the center with a knife, about 1 hour. Set aside until cool enough to peel. Peel the potato and puree the flesh in a food processor. Reserve ⅔ cup of the puree. Leave the oven on. (You can save the rest for up to 1 week, tightly covered and refrigerated.)
Generously butter six straight-sided ½-cup ramekins or individual soufflé molds.
Return the sweet potato puree to the food processor and add the ricotta, egg yolks and salt. Process to a smooth puree.
Roll the prosciutto slices into a tight bundle and slice crosswise into very thin strips. Scatter them with your fingertips to keep them from sticking together.
Beat the egg whites in a large, clean bowl until frothy. Add the cream of tartar and continue beating until stiff peaks form. Do not overbeat.
Add about ¼ cup of the sweet potato-ricotta puree to the egg whites and gently fold in. The best way to do this is with a handheld balloon whisk or a spatula. In either case, cut straight down through the puree and the egg whites, scrape the bottom and lift the egg whites over the puree. Turn the bowl a quarter turn and repeat. Keep doing this until the puree is fully incorporated, 3 or 4 times.
Add the remaining sweet potato-ricotta puree and fold it in the same way. When you’re done, the puree should be evenly distributed, but there may be small patches of egg whites remaining. Do not overmix, or the egg whites will lose too much volume.
Scatter the prosciutto strips over the top and very gently fold them in. Do not worry too much about distributing them evenly.
Using a large soupspoon, evenly divide the soufflé mixture among the buttered ramekins. Depending on how well the egg whites were beaten, you may have some of the mixture left over. Either bake in another ramekin or discard.
(The recipe can be made to this point, covered tightly with plastic wrap and refrigerated for up to 2 hours or frozen for up to 2 weeks. The soufflés can be baked straight from the refrigerator. If frozen, remove the plastic wrap immediately and let stand at room temperature for 30 minutes before baking.)
Put a jelly-roll pan in the oven and arrange the ramekins on it. Bake until the tops are puffed and dark brown in spots, 25 to 30 minutes. The surest sign of doneness is when the soufflés become extremely fragrant. Do not overbake, or the centers will be dry.
Remove from the oven and serve immediately.
A good soufflé is a transcendent bit of cooking, delivering a wallop of flavor on a breathy whisper. It is intense yet ethereal, profound but insubstantial. True, it has a reputation for being the diva of the food world—risky and temperamental. But in reality it’s a surprisingly tough little rascal, and its rewards far outweigh the bit of extra trouble.
Did you know that a soufflé can be put together in less than 20 minutes? That you can make it ahead and freeze it until just before dinner? Now I’ve got your attention.
The magic of the soufflé is how its fairly normal-looking batter puffs and fills with air while baking. Like so many other bits of kitchen wizardry, that loft comes thanks to the egg—specifically, the egg white, which is a combination of water and protein and not much else. When egg whites are beaten with a whisk, the proteins, which are naturally curled up in little balls, relax and unfold. As they do, they connect with other proteins and form bonds. These connected strands leave small gaps—tiny bubbles, really—filled with air. When the soufflé is heated, the air expands inside the bubbles and the soufflé puffs. The water evaporates, leaving nothing behind but the inflated thin framework of protein strands—and whatever else you add to them, of course.
No matter how interesting they may be scientifically, there’s nothing very compelling flavor-wise about plain egg whites. Traditionally, the addition of flavor begins with some kind of flour-based paste, such as a thick white sauce. But there is nothing flavorful about that either. You can get the same effect—and a lot more flavor—by using other kinds of pastes: a puree of roasted sweet potatoes, for example, or a soft cheese such as ricotta or fresh goat cheese. To this base, egg yolks are usually added. They make the soufflé a little richer, but they also thin the paste enough that it won’t collapse the egg whites when they’re folded in.
Although the base carries the flavor, by far the trickiest part of making a soufflé is the egg whites—and they are probably the reason for much of the recipe’s reputation for being difficult. They need to be beaten—but just enough. They need to be handled gently. Most cooks have some kind of electric mixer for beating egg whites, either a handheld one or a big stand mixer.
After only a couple of minutes, you’ll notice that the egg whites are beginning to hold a shape: soft, billowing mounds. Keep going. Within a minute or two, you’ll notice that the whites are forming something that actually looks like a peak (as opposed to a small hill). Lift the beaters from the bowl: the whites will probably form a point at first, then almost immediately collapse back into the bowl. These are called “soft peaks,” and they aren’t stable enough to withstand the heat of the oven. When the peaks are stiff enough that they hold their sharp points—both in the bowl and from the beaters—you’re done. The beaten whites should be shiny and glossy. Roll the bowl around; there should be no loose whites in the bottom of the bowl. If you want to make certain they’re done, prop a whole egg on the whites—they should be firm enough to support it.
Don’t overdo the beating, though. Stiffer is not better. You can beat in so much air that the structure no longer contains bubbles, and you’ll be left with a clumpy, grainy mess that looks like Styrofoam. If this happens, you have to start over.
When beating egg whites, it’s important to have a very clean metal bowl and beaters. Any trace of fat will interrupt the linking of the protein chains, and the bubbles won’t inflate. Don’t use plastic or wooden mixing bowls, which are so porous that you can never be sure they are completely free from fat.
Stiff-peaked egg whites are so incredibly stable that you can spoon the fully prepared soufflé into a ramekin, cover it tightly with plastic wrap and refrigerate it for a couple of hours with no ill effects. You can even freeze a soufflé for up to a month. Just pull it out about 30 minutes before baking to let it warm up slightly so the dish won’t shatter in the oven. (If you use Corning Ware or Pyrex, you don’t even need to do this.) Be sure to remove the plastic wrap as soon as the soufflé comes out of the freezer. Do it later, when the egg whites have defrosted and are more delicate, and you risk an embarrassing deflation.