Wash the potatoes thoroughly, cut into pieces and cook in boiling salted water for about 20 minutes. In the meantime, wash the dill, shake dry and chop finely, except for a few flags for garnishing
Melt butter in a pot. Sweat flour in it while stirring for 2-3 minutes. Stir in mustard. Deglaze with vegetable stock and milk, bring to the boil and simmer over low heat for about 5 minutes, stirring occasionally. Add chopped dill and prawns. Season to taste with salt and pepper. Let simmer at low heat
Cook the eggs in boiling water for 6-7 minutes. Drain potatoes. Drain eggs, quench, peel and arrange on plates with potatoes and sauce. Garnish with dill flags and pepper