For the Sorbet, place raspberries (or blackberries if using) in the freezer for 3 hours or until frozen. Place the frozen raspberries and Aranciata in the bowl of a food processor fitted with blades. Whiz until smooth and creamy, serve or refreeze until required.
For the brioche, combine yeast and water in a jug and set aside for 10 minutes or until frothy. Place yeast mixture, 500g flour, sugar, lemon and orange zest and 3 eggs in a stand mixer fitted with the dough hook. Knead on low speed for 3 minutes to combine. Add a pinch of salt and knead for a further 6-7 minutes until smooth.
With the motor running, add butter, one piece at a time, making sure each piece is incorporated before adding the next, until smooth and elastic. Add the remaining flour as needed to create a soft dough that is not sticky.
Transfer to a floured bowl, cover with plastic wrap and set aside for 1.5 hours or until doubled in size.
Preheat oven to 180°C and line 2 baking trays with baking paper. Knock back the dough, knead lightly for 30 seconds, then divide dough into 6 mandarin size pieces and 6 walnut sized ones (or you can go even smaller and make more brioche). Roll each piece into a smooth ball and place the smaller ball on top of the bigger one (it should look like an odd 8 shape) and lay on prepared baking trays.
Cover trays with clean tea towels and set aside for a further 20 minutes or until slightly risen. Combine remaining egg and milk in a small bowl. Brush over brioche, then bake for 15-18 minutes until golden and cooked. Transfer to a rack to cool. Serve the cooled brioche with the sorbet.