Clean the spring onions, rinse and cut into rings. Peel the potato and cut into fine cubes. Heat butter in a saucepan, sauté spring onions and potatoes for 1 minute. Sauté peas for another 1 minute.
Extinguish with wine, fish stock and clear soup, simmer for 10 min on low heat.
In the meantime, rinse cooled matie, cut in half lengthwise and cut into bite-sized pieces. Coarsely crumble pumpernickel. Stir sour cream with dill and horseradish.
Remove 4 tablespoons peas from soup. Grind remaining soup, pass through a sieve. Mix in dill cream (except for 4 tsp for garnish). Heat soup repeatedly without bringing to a boil to prevent sour cream from flocculating.
Toast pumpernickel crumbs in a frying pan without fat over medium heat.
Divide herring pieces and 1 tablespoon peas evenly among preheated soup plates. Pour hot soup over, garnish each with 1 tsp sour whipped cream and pumpernickel crumbs. Serve immediately.
Mix dill cream
mix. A good tablespoonful of the herring-whipped cream mixture is then added directly to the hot soup in each plate.