Place the sugar in a pan and pour 1 1/4 cup water. Bring to the boil, stirring until the sugar is dissolved
Take the pan off the heat, add the flowers and leave to infuse (steep) for 1 hour. If time permits, chill the syrup in the refrigerator before using.
Process the strawberries in a food processor or in batches in blender, then press the puree through a large sieve into a bowl.
Pour the puree into a freezerproof container, strain in the syrup and freeze for 4 hours, or until mushy. Transfer to a food processor and process until smooth. Whisk the egg white until frothy, and stir into the sorbet. Spoon the sorbet back into the container and freeze until firm.
Serve in scoops, piled into tall glasses and decorate with sprigs of lavender flowers.