Not a common soup for everybody, but it's very tasty and easy to prepare, but you have to like mustard.
This basic recipe is for 4 persons.
30 Gr real butter
40 Gr flour
1 liter chicken stock (cubes)
1 Dl crème fraîche
2 Egg yolks (dooier)
4 Table spoons of mustard, with grains (not the smooth one)
Melt the butter in a pan and stirr the flour (I always sift the flour) for about 5 minutes.
Then, keep stirring, add little by little the stock until smooth.
Bring to the boil for 2 minutes (or if you want to finish the soup later, then re-heat the stock again)
Mix the crème fraîche with the egg yolks. (Don't put it yet in the soup).
Now put the mustard in and finally the egg/crème mixture.
Ready to serve.