150 g "white" vegetable broth
--- from parsley roots, celery root, leeks etc
75 g horseradish, peeled, freshly grated
--- [if you are sensitive, wear a mask and only breathe through the nose]
150 g whipping cream
25 g white bread, diced
5 g mustard seeds, finely ground
1/4 TS salt
1/4 TS white pepper, finely ground
1/2-1 TB water
1/2 egg yolk, slightly beaten
Bring broth and horseradish to a boil. Simmer until the broth is reduced by 1/3. Add the whipping cream and simmer for 15-20 minutes, stirring frequently. Gradually add the bread, stirring constantly until it is completely dissolved. Mix mustard seeds, salt and pepper with water until smooth. Add mixture to the horseradish, stir well. Remove from heat and stir in the egg yolk.
Immediately put the horseradish into a tightly closable container. Let cool in ice water: The quicker it cools, the more durable it is (max 2 weeks in the refrigerator). Content of open jars should be used within 3 days.