A creamy, lightly sweetened, soft-serve style vanilla bean frozen yogurt made with Greek yogurt. Adapted from [Baking Bites|http://bakingbites.com/2012/07/homemade-frozen-greek-yogurt/].
In a saucepan over medium-high heat, bring water and sugar to a full boil and boil about 90 seconds or until all the sugar has dissolved and you have a thick, clear syrup. Turn off heat.
In the clean, dry bowl of a stand-mixer fitted with the whisk attachment, beat the egg whites to soft peaks at medium-high speed. Reduce the speed to low and stream the hot sugar syrup slowly into the beaten egg whites. When you have added all the syrup, turn the mixer up to high and continue beating until the mixture forms a thick, glossy meringue and the sides of the bowl are no longer hot to the touch, but just warm (in my mixer, this took about 5 minutes).
Fold the Greek yogurt and vanilla into the meringue until well incorporated. Transfer the mixture straight into the bowl of your ice cream maker and churn according to manufacturer's instructions until frozen, but still soft-serve texture, not firm. (I churned mine with my KitchenAid Ice Cream Maker attachment for 10-12 minutes).
Serve promptly with toppings and mix-ins as desired. Store any leftovers in freezer. Soften before reserving.