For a frozen yogurt that’s dense and creamy—not icy and rock-hard like most versions—the key was controlling the water in the base so that the number of large ice crystals that formed during freezing was minimized. Since Greek yogurt is strained of excess liquid during processing, it seemed like a logical starting point, but it produced a chalky frozen yogurt. We got much creamier results when we used plain whole-milk yogurt that we strained of excess liquid ourselves. We also found that swapping in a few tablespoons of Lyle’s Golden Syrup for some of the granulated sugar played an important role. Unlike granulated sugar, which is made up of larger sucrose molecules, Lyle’s is about 50 percent invert sugar, which is made up of smaller glucose and fructose molecules. These smaller molecules are much better at depressing freezing point, so more of the water in our frozen yogurt base stayed in liquid form, delivering a frozen yogurt that not only contained fewer ice crystals but also was more scoopable straight from the freezer. The final step in managing the water was to trap some of it using unflavored gelatin. By dissolving and heating just 1 teaspoon of gelatin in a portion of the strained whey, we prevented even more water molecules from joining together and forming large ice crystals.
This recipe requires draining the yogurt for 8 to 12 hours. We prefer the flavor and texture that Lyle’s Golden Syrup lends this frozen yogurt, but if you can’t find it, you can substitute light corn syrup. Any brand of whole-milk yogurt will work in this recipe. You can substitute low-fat yogurt for whole-milk yogurt, but the results will be less creamy and flavorful.
1. Line colander or fine-mesh strainer with triple layer of cheesecloth and place over large bowl or measuring cup. Place yogurt in colander, cover with plastic wrap (plastic should not touch yogurt), and refrigerate until 1 1/4 cups whey have drained from yogurt, at least 8 hours or up to 12 hours. (If more than 1 1/4 cups whey drains from yogurt, simply stir extra back into yogurt.)
2. Discard 3/4 cup drained whey. Sprinkle gelatin over remaining 1/2 cup whey in bowl and let sit until gelatin softens, about 5 minutes. Microwave until mixture is bubbling around edges and gelatin dissolves, about 30 seconds. Let cool for 5 minutes. In large bowl, whisk sugar, syrup, salt, drained yogurt, and cooled whey-gelatin mixture until sugar is completely dissolved. Cover and refrigerate (or place bowl over ice bath) until yogurt mixture registers 40 degrees or less.
3. Churn yogurt mixture in ice cream maker until mixture resembles thick soft-serve frozen yogurt and registers about 21 degrees, 25 to 35 minutes. Transfer frozen yogurt to airtight container and freeze until firm, at least 2 hours. Serve. (Frozen yogurt can be stored for up to 5 days.)