How to make
Cut the onions finely and saute them with the lid on medium heat in the melted butter. Add the mustard, stir and sprinkle it with paprika. Stir again and add the broth.
Allow to boil for 5-10 minutes. Gradually add the grated cheese to the soup and stir until completely dissolved. Dissolve the starch in a bowl with the milk.
Pour this in a thin trickle into the ready soup and stir. After it comes to a boil, simmer for 2-3 minutes, stirring occasionally.
Serve with croutons and a scoop of cream.