Wash the cucumber and cut it into strips around the core with a peeler. Season with salt. Mix sour cream and cornstarch. Prepare noodles according to package instructions. Meanwhile bring fish stock to the boil. Stir in sour cream and horseradish and bring to the boil again.
Wash the dill, dab dry and pluck all but a few flags from the stalks to garnish. Fold dill into the sauce. Arrange noodles and gherkins. Drizzle with sauce and sprinkle with caviar and crayfish. Garnish with dill and possibly crayfish (with shell)