Wash the potatoes well and cut them in half. Don't peel. Grate three quarters of the potatoes and finely chop the rest.

Squeeze all the liquid out of the potatoes really well! Form them into a thick pancake shape and season lightly with salt (the cheese is also a little salty so, no need to over season).

Melt 1 tablespoon of butter in 1 tablespoon of oil in a large non-stick pan. Cook the rosti for about 10-12 minutes on each side until golden brown. Top each side with grated cheese before flipping. Note: You can flip the rosti or turn it out onto a plate and then cover with another plate to make flipping over easier and neater.

The rosti should be crispy on the outside and soft on the inside.

Serve warm, topped with fresh chives and sour cream.