500 grams blueberries
finely grated zest 1 orange
¾ cup sugar
2 tablespoons Crème de cassis or other berry liqueur
1 cup thick plain yoghurt
Place all the ingredients, except the yoghurt, in a food processor and process until smooth. Add the yoghurt and process again.
Pour into a shallow metal freezer-proof container and freeze until frozen.
Chop the sorbet into rough chunks and in batches, place in a blender or food processor and process until smooth.
Tip back into the container and freeze again. Makes about 4 cups