Place the blackberries in the bowl of a food processor. Process until smooth. Strain the blackberries through a fine mesh sieve set over a large mixing bowl. Using the back of a spoon, press the mixture against the sieve to extract all the juice. Discard the seeds and any pulp.

Add the yogurt to the blackberry juice and stir to combine. Add about 3/4 cup of honey and taste for sweetness. You may need more honey depending on how sweet the blackberries are. I used just under 1 cup. Add vanilla if desired and blend until smooth.

Process in an ice cream maker according to manufacturer instructions. Serve immediately if you prefer a soft serve consistency or freeze until firm. If frozen remove from the freezer about 15 minutes before serving.