First some general instructions for making frozen fruit yogurts: Begin preparation as least 5 hours before serving time. Freeze all of the fruit in a single layer on a sheet pan. A few minutes before service, pulse the frozen fruit a few times in a food processor, then process continuously, scraping down the work bowl until the fruit is finely chopped. Add plain yogurt and any additional ingredients. Process just until mixture becomes smooth; taste for sweetness level.
To make 1 quart of frozen yogurt: Whisk 4 Tbsp of granulated sugar into 32 ounces of vanilla yogurt (generally sold in 8 oz. containers); then transfer the mixture to your ice cream machine for freezing.
To make frozen banana-apple yogurt: Peel 3 small bananas; peel, core, and chop 2 medium Golden Delicious apples. Proceed as in the general instructions, above, adding 1/2 cup plain yogurt, 4 tsp fresh lemon juice, and confectioners' sugar, to taste..
To make the black-raspberry ice cream: Stir puréed & strained raspberries into the cooled custard base along with a Tbsp of Chambord (a sophisiticated, French black-raspberry liqueur) OR an orange-flavored liqueur you prefer – being careful not to add too much because alcohol acts as an antifreeze. Chill the base well in the refrigerator; then transfer to the machine’s freezing compartment.
Enjoy!