I have to hand it to the frozen yogurt people—they have a hell of a racket.
Few chains do as good a job of making us feel like we're in control as frozen yogurt stores. Think about every one of those serve-yourself, pay-by-the-ounce fro-yo places, and how much autonomy you have in every transaction. You swirl your own yogurt. You only take as much as you want. You have a dozen-plus options of flavors. Toppings? As many or few as you'd like in whatever combination you desire. Look at all the choices you have!
Now look at the cup they give you for your yogurt, and how puny a serving looks if you don't swirl it to (or over) the top. Look at how low those prices are per ounce. Do you know what an ounce feels like? Me neither. And the topping surcharges: are you keeping track?
And then you pay up: $8 for a bowl of candy-coated yogurt goop that, at the end of the day, doesn't taste much like yogurt, does it?
I'd like to suggest another option—that you ditch store bought frozen yogurt and consider making your own. If you really love frozen yogurt—and I mean real frozen yogurt—there's nothing better than homemade. And all it requires is two ingredients.
What is Frozen Yogurt?
Frozen yogurt is just ice cream by another name: a frozen dairy dessert made with yogurt instead of milk and cream. You could, if you wanted, make frozen yogurt with nothing more than yogurt itself. Stick some plain full-fat yogurt in an ice cream machine and give it a churn. 20 minutes later you'll find yourself with a slushy soft serve that needs nothing more than a pinch of salt, drizzle of olive oil, or splash of balsamic vinegar.
But if you harden this yogurt in a freezer it'll solidify into a brick. To make a frozen yogurt you can scoop like ice cream, you need to add sugar. As with ice cream and sorbet, the more sugar you add, the softer your yogurt will be. Sugar molecules get in the way of growing ice crystals, keeping your frozen dessert smooth and creamy.
Most fro-yo shops buy their yogurt base wholesale, many from a single manufacturer called YoCream, a division of the Dannon yogurt company. Here's what goes into YoCream's plain non-fat frozen yogurt base (they don't have a non-non-fat version):
Pasteurized Non Fat Milk, Liquid Sugar (Sugar, Water), Pasteurized Sweet Cream Buttermilk, Corn Syrup, Pasteurized and Cultured Non Fat Milk, Whey, Non Fat Dry Milk, Contains Less Than 1% Of Milk Protein Isolate, Cellulose Gum, Guar Gum, Carrageenan, Modified Food Starch, Pectin. Contains the following live and active cultures: S. thermophilus, L. bulgaricus, L. lactis, L. acidophilus and Bifidobacterium.
Skim milk and sugar make up the base's mass. Buttermilk and cultured milk add live yogurt cultures, and corn syrup, powdered milk, whey, and stabilizers all enhance texture, turning what would otherwise be an icy slush into something creamy.
Since fro-yo shops market their products as low-fat and low-calorie, they need all those stabilizers to make up for the higher amounts of sugar and fat in homemade frozen yogurt. As long as you're willing to handle a moderate amount of sugar and fat, you don't need them.
How to Make It
The best frozen yogurt recipe I've ever seen comes from my friend Ethan Frisch, formerly the chef of Guerilla Ice Cream. It's also the easiest: take a quart container of full-fat plain yogurt, add a cup of sugar and a pinch of salt, and churn. That's it. You'll be shocked at how fresh and fruity it tastes—the natural berry flavor of the yogurt's lactic acid enhanced by sugar.
From a physics standpoint, yogurt is a gel: that is, liquid milk suspended in a solid state by a loose matrix of polymers. In jello, those polymers are gelatin molecules; in yogurt, it's coagulated milk proteins.
That means despite yogurt's custardy texture, from the ice-cream maker's standpoint, it's just another kind of milk. A lot of yogurt has more fat and less water than an equal volume of milk, and those coagulated proteins do add some creaminess, but the only way to get your frozen yogurt actually creamy is to add a good amount of sugar—more than you might for ice cream, which has extra fat and egg yolks to help enhance texture.
When I make frozen yogurt, I treat it like sorbet, following a master ratio of one cup of sugar for every four cups of liquid.* This is why you'll sometimes see "yogurt sorbet" on dessert menus—that's how pastry chefs often think of frozen yogurt, and the comparison is apt. Frozen yogurt isn't as naturally creamy as ice cream, nor should it be—it's best with a cleaner, lighter sorbet-like texture to preserve its light tangy flavors.
* Technically the ratio for frozen yogurt winds up more like 3 3/4 cups of yogurt to a cup of sugar, as most quart-sized containers of yogurt fall short of a full four cups of yogurt. For you pastry people who prefer weight measurements, that's seven ounces of sugar to 32 ounces of yogurt.
We don't go into nutrition much on Serious Eats, but if you're wondering, a half-cup serving of this frozen yogurt has about 160 calories and four grams of fat—heavier than the fat- and sugar-free stuff you'll find at fro-yo shops, but not exactly a fat bomb. And the flavor upgrade is incomparable.
And because I know you'll ask: yes, full-fat yogurt is a much better choice than low-fat or skim. Not only will you get a creamier texture with whole milk yogurt, but the flavor will be brighter and more balanced; skim milk makes for a harsh, tart yogurt that doesn't take well to dessert.
What About Greek Yogurt?
Greek-style strained yogurt has more fat and protein and less water (in the form of whey) than plain yogurt. Since fat and protein enhance creamy texture, why not make frozen yogurt with Greek yogurt? You could, but I think the Greek stuff does too good a job—it's too creamy, so much so that when frozen it feels like you're chewing on sour cream.
That said, Greek yogurt has some benefits. You could cut it with plain yogurt to make a richer frozen yogurt akin to ice cream. Or you can take advantage of the yogurt's lower water content to add other flavorings.
Think of it this way: you get to replace excess whey in yogurt with a more flavorful water-type liquid. Citrus juice is one option; flavored syrups like ginger are another. But my favorite flavoring is a dry white wine. Wine brings its own kind of tartness and fruity notes, making the yogurt taste even more yogurt-y while adding a whole new dimension of flavor. I can't think of anything better for yogurt lovers.
Flavoring Your Yogurt
If you want to add other flavors to your yogurt, you have three ways to do so: infusion, mix-ins, and toppings.
Infusions are the easiest. Have some lime or orange zest? Grate it right into your yogurt, let it sit for a couple hours, and churn. Or add mint leaves or grated ginger, let your yogurt sit overnight, and then strain the chunks out before churning.
Mix-ins like wine, spirits, fruit purée, or jam are also a snap. Swap out as little as a few tablespoons of yogurt for as much as half the total volume depending on the strength of the mix-in. But take note that the proteins in yogurt have a way of dulling other flavors, so the bolder your mix-ins, the better.
But my favorite frozen yogurt flavorings come in the form of toppings that let the yogurt stay true to itself. My friend Ethan was a big fan of grated halvah. Luxardo maraschino cherries are a favorite of mine. Drizzles of olive oil, pomegranate molasses, or balsamic vinegar all taste great, too, as do segments of citrus, chopped candied ginger, roasted nuts, or fresh berries.
The key with any flavoring is to stick with additions that have some savory or sour flavors to balance out the yogurt's sweetness. Remember: real frozen yogurt is all about balance: sweet and tart, fresh and creamy, milky and fruity. Now doesn't that sound better than the blandly swirly stuff you find in stores?