1.Boil, steam or microwave potatoes until just tender. When cool enough to handle, peel skins, then cut flesh into 1cm (½-inch) cubes.
2.Preheat oven to 160°C (140°C fan forced). Grease a deep 24cm x 35cm (9½-inch x 13¾-inch) baking pan, line base and sides with baking paper, extending paper 7cm (2¾-inches) above sides.
3.Meanwhile, heat oil in a large frying pan over medium heat. Add chorizo and onion, cook, stirring, for 5 minutes or until chorizo is browned. Cool 10 minutes.
4.Combine potatoes, half the chorizo mixture, rocket, parsley and cheese in baking pan.
5.Whisk eggs and cream together in a medium bowl, season to taste. Pour over potato mixture, top with remaining chorizo mixture. Bake, in oven, 35 minutes or until set. (To check, insert a skewer; no wet egg mixture should be visible.) Cool in pan.
6.Turn frittata onto a chopping board, trim edges. Cut into 3.5cm x 4.5cm (1½-inch x 1¾-inch) pieces. Turn pieces right-way up to serve. Serve topped with extra rocket and accompany with wedges.
To reheat, place frittata pieces close together on a baking-paper-lined oven tray in a preheated 160°C (140°C fan forced) oven for 25 minutes or until heated through.Note