1. Process strawberries in a food processor or blender 30 seconds or until smooth, stopping to scrape down sides. Pour strawberry puree through a fine wire-mesh strainer into a large bowl, pressing with back of a spoon. Discard solids. Add buttermilk, sugar, and vanilla to puree; stir until well blended. Cover and chill 1 hour.
2. Pour strawberry mixture into freezer container of a 1 1/2-qt. electric ice-cream maker, and freeze according to manufacturer's instructions. (Instructions and times may vary.) Garnish, if desired.
*1 (16-oz.) package frozen strawberries, thawed, may be substituted.