Cook marbled beef in sous-vide with salt, pepper and butter for 7.5 hours at a temperature of 56 degrees.
Cut the parsley root into cubes and cook in milk until tender. Then, drain the milk and pierce the root in a blender with the addition of cream.
In a saucepan, combine Demi-glace sauce, kvass must, red wine and chicken broth. Bring to a boil and add the soaked morels.
Fry onions until golden brown, add white wine and simmer a little. Add kvass wort, honey, granulated sugar and Demiglas sauce. Simmer for 30 minutes over low heat. Punch everything in a blender.
Parsnip root cut into slices and scalded with boiling water, strain and deep-fry until golden brown.