Cook potato in a large saucepan of boiling, salted water for 10-12 minutes or until just tender. Drain. Reduce heat to low. Return potato to pan, roughly mash. Remove from heat set aside.
Meanwhile, bring a saucepan of water to the boil. Cook buckwheat in a non-stick frying pan over medium heat, stirring, for 2 minutes or until toasted. Cool for 5 minutes. Add buckwheat to water. Reduce heat to medium-low. Simmer for 5 minutes or until al dent. Drain.
Heat 2 teaspoons of oil in a small frying pan over medium heat. Add onion, cook for 3-4 minutes or until soft. Add seasoning, cook stirring for one minute for until fragrant. Remove from heat. Add onion mixture. Buckwheat, zucchini, carrot and coriander to potato. Stir to combine. Shape into patties using a 1/4 cup measure.
Place quinoa flakes in a shallow bowl. Dip patties in quinoa to coat, shaking off excess. Refrigerate for 15 minutes. Heat remaining oil in a large frying pan over medium heat. Cook patties in batches, adding more oil if required, for 3-4 minutes on each side or until golden and heated through. Serve with minted yoghurt, a squeeze of lemon, mango chutney and a green salad.