Pre-heat the oven to 200°C.
Boil the potato halves in salted water for 4-5 minutes, then drain and allow to cool until they are cool enough to handle. Grate into a large mixing bowl.
Blanche the vermicelli for 1-2 minutes until soft, then drain and mix with the potato. Add seasoning, cornflour and the chives and mix well.
Heat a non-stick frying pan over a medium-high heat until hot then add some of the clarified butter. Place a 7cm metal ring in the middle of the frying pan and spoon a couple of tablespoons of the rosti mixture into it, pressing down well to even it out and promote a crust on the bottom. Cook over a reduced heat for a few minutes, then flip and cook for a further minute.
Arrange on a lined baking tray and continue to make rostis using up the mixture in the same fashion and arranging on a baking tray when done. Bake in the oven for 5-7 minutes until golden brown. Remove and arrange stacked on greaseproof paper, then serve.
To make clarified butter, simply melt butter in a saucepan and allow to cool. Once the water has evaporated, skim off any solids that float to the surface. Pour the clarified butter into a large bowl, being careful not to include any of the milk solids. This butter can be used to cook at higher temperatures without burning.