Preheat the oven to 200°C.
Squeeze the liquid out of the grated potato using a clean tea towel and season with salt and pepper.
Heat butter and oil in a small ovenproof pan and press half the potato into the base.
Layer Brie slices over the potato and cover with the remaining grated potato.
Fry the rosti for two minutes on each side until golden-brown.
Bake the pan in the oven for six minutes until the potato is tender.
Heat olive oil in a separate pan and fry the steak to your preference, then rest for five minutes.
Serve the steak with the finished rosti and blanched green beans.