Place raspberries, yogurt, sugar and vanilla in a food processor and process until smooth.
Transfer the mixture to an ice cream maker (or see "No Ice Cream Maker?" below). Freeze according to manufacturer¿s directions, or until desired consistency. Add chocolate chips during the last 5 minutes of freezing. Transfer to an airtight container and freeze until ready to serve. No Ice Cream Maker?Pour the mixture into a 9-by-13-inch pan and place in the freezer. Stir every few hours, until the mixture is firm along the edges and semi-firm in the center, 2 to 6 hours (using frozen berries will shorten the freezing time). Transfer to a food processor and process until smooth. Transfer to an airtight container, stir in chocolate chips, cover and freeze until ready to serve.