Put the ingredients for the pasta dough in a food processor and knead into a smooth dough. The dough hooks of the hand mixer also work. Then wrap the dough in cling film and let it rest at room temperature for about 30 minutes.
In the meantime, wash and clean the vegetables. Cut the leek, celery and carrots into fine cubes. Finely chop the spinach. Melt the butter in a pan, fry the onion in it. One after the other, add the carrots, celery, leek and finally the spinach and cook until it has the desired firmness. Transfer the vegetables to a bowl, allow to cool a little, then stir in the egg yolks and breadcrumbs. The mass shouldn't be too soft. Season well to taste with the spices. Let everything cool down well.
Roll out the dough thinly on a floured work surface or turn it through the pasta machine. Put the filling on the dough and shape into ravioli. I have molds with which I can cut out the dough and shape it at the same time.
Cook in salted water until they float to the surface.
For the sauce, melt the butter and sauté the onion in it. Add flour and toast briefly. Then pour in the milk, stir vigorously so that there are no lumps and let it simmer on a low flame. Now season with the spices to taste and finally fold in the chives.
Depending on your taste, you can also serve it with sage butter.