Start with frozen fruit and you'll have a delicious, fresh, tasting
frozen yogurt 5 minutes later. For convenience, you can use
commercially packaged. mixed frozen fruit; strawberries, bananas and
blueberries (alone or as a combination) are delicious, but avoid
seedy fruits, such as raspberries.

In a food processor, combine frozen fruit and sugar. Using an on/off
motion, process until coarsely chopped.

Stir together yogurt and lemon juice. With the machine running,
gradually pour the yogurt mixture through the feed tube. Process
until smooth and creamy, scraping down the sides of the work bowl
once or twice.

Scoop the frozen yogurt into freezer-proof serving dishes, cover and
freeze 15 to 30 minutes to firm up slightly.

From an article by Susanne A. Davis in The San Mateo Times, 5/25/93.