1.Boil, steam or microwave potato and kumara until tender; drain. Mash potato and kumara with butter in medium bowl until almost smooth. Cool 20 minutes.
2.Stir salmon, egg yolk and herbs into potato mixture. Shape mixture into eight patties. Cover; refrigerate 1 hour.
3.Preheat oven to 200°C (180°C fan-forced). Oil oven tray; line with baking paper.
4.Coat patties in breadcrumbs; place on tray. Bake about 40 minutes or until browned lightly. Serve with a rocket salad and lemon wedges, if you like.