Watermelon and boysenberry granita with melon and sparkling shiraz

For watermelon and boysenberry granita, combine boysenberries and sugar in a heatproof bowl placed over a saucepan of simmering water, cover with plastic wrap and cook until mostly liquid (1 hour). Strain through a fine sieve, pressing lightly on solids to yield 400ml liquid, then refrigerate until chilled (1 hour). Meanwhile, blend watermelon in a blender until liquid, then strain through a fine sieve, pressing lightly on solids to yield 1 litre juice. Combine boysenberry syrup with watermelon juice, then freeze in a large shallow tray, scraping with a fork every few hours, until completely frozen (6 hours-overnight).

Combine watermelon balls, sugar and vanilla in a bowl and refrigerate until sugar dissolves (1 hour).

Place chilled watermelon and berries in chilled bowls, pour over a little sparkling wine to taste, top with granita and serve.