Peel the boiled potatoes and press through a ricer into a bowl. Add the egg yolks, salt, pepper and flour to the potatoes and mix well. Remove from the bowl and knead by hand to form a compact dough.
Clean the chanterelles and finely dice the ½ onion. Heat some oil in a large frying pan. Add the onions and sauté. Add the chanterelles, season with salt, cover and simmer over a medium heat for 5 minutes. Stir in the parsley.
Now prepare the béchamel sauce for the Mascarpone creme (create a roux sauce with the butter and flour, then stir into the lukewarm milk and cream mixture and simmer for 10 minutes). Season to taste with salt and pepper and then just before serving stir in the Mascarpone.
For the sage foam peel and finely dice the ½ onion. Sauté the onion in a frying pan with butter. Now quench with the vegetable stock. Put the sage in the sauce and bring to the boil. Next leave the sauce to simmer for 5 minutes. Then add the cream and simmer for a further 10 minutes. Remove the sage and season with salt and pepper. Add a little cold butter to the sauce and mix to a froth with a hand blender.
The gnocchi dough is now cut into several pieces, with each piece being turned into a roll. Regularly sprinkle with a little flour to ensure that you are able to work the dough. Now cut gnocchi-sized pieces from the roll and place in gently simmering salted water. As soon as the gnocchi rise to the surface they can be skimmed off.
Put a little of the Mascarpone creme on a plate, place the gnocchi on top and garnish with the fresh chanterelles and sage foam.