Herring in mustard refueling

Salads and snacks 
from fish
Herring in mustard refueling

Onions are finely chopped, lowered for several seconds into boiling water and cooled quickly. Prepared onions are laid flat on the herring fillets, rolled up with rolls, packed tightly in a non-oxidizing dish, then filled with mustard dressing and allowed to stand in a cool place (4-8 ° C) for 8-10 hours. 
When feeding, the herring is watered by the same dressing and sprinkle with chopped green onions and finely chopped greens. 

Herring (fillet) 150-200 g, onions 1-2 heads, onion green 50 g, mustard filling 3/4 st.