Add the frozen strawberries, agave nectar (or honey), yogurt and lemon juice to the bowl of a food processor. Process until creamy, about 5 minutes.
Serve the frozen yogurt immediately or transfer it to an airtight container and store it in the freezer for up to 1 month.
I prefer a more tart frozen yogurt, but you can add additional agave nectar or honey if you want a sweeter-tasting dessert.
Fresh strawberries can be used in place of frozen, however the fresh strawberries must be frozen solid.