My almost 6 year-old (!) and I made this raspberry frozen yogurt (with no ice cream maker) after watching jamie oliver make a similar one with mango. Here's that recipe. The trick is to use frozen fruit. We also added a bit more honey and sugar because the raspberries were pretty tart. This was all in the food processor and took no time at all. We just played with the proportions until it seemed really thick—like it would freeze well. White sugar made it grainy, but after it froze overnight, the graininess was gone. We ate it right away and it was semi-soft, after freezing overnight it was perfectly scoop-able. I always have a ton of frozen fruit on hand because I am crazy about not wasting it, it's so great to put in smoothies, but I never thought to make it into a frozen yogurt ice cream type treat. It's lovely between two lemon ginger cookies.