Peel pear, and cut into chunks. In a food processor or blender, pulse pear until coarsely chopped. Pour through a wire-mesh strainer into a bowl, discarding pulp. Set juice aside.
For each serving, add 1 tablespoon prickly pear juice and several blackberries to each glass; fill with champagne.
Note: Two cups raspberries may be substituted for one prickly pear. In a food processor or blender,process raspberries until smooth. Pour through a wire-mesh strainer into a bowl, discarding seeds. Set juice aside. Proceed as directed.