Peel the carrots and cut into small pieces. Sweat butter in a large pan and fry the carrots in it. Add mushrooms and fry brown over medium heat. Season already now with salt and pepper. Wash and clean the large fennel bulb (better to use two for small ones) and also cut into small pieces. Add to the carrots and mushrooms and fry them. Meanwhile, roughly chop the walnuts.
When the vegetables are almost firm to the bite, add the cream or crème fraîche and simmer on a low flame until the desired firmness is achieved. Possibly add a little water if the sauce boils down too quickly. Add a dash of orange juice and the walnuts and season with salt and pepper to taste.
Thin spaghetti or other noodles as well as Parmesan to sprinkle with taste also taste good.
Tip:
The vegetarian dish becomes slightly vegan if you use soy cream instead of cream / crème fraîche or mix a vegan béchamel sauce.