Defrost the puff pastry. Roll out the layer, 0.5 cm thick.
Cut out circles with a glass, cut out the same number of rings with a mold of a smaller diameter.
Fold in two different blanks and brush with yolk.
Bake in an oven preheated to 180 degrees C for 5-7 minutes, until golden brown. Take out and let cool.
Wrap the beets in foil and bake in the oven until tender. Remove to cool and clean.
Grate on a fine grater. Season with a little salt and season with mayonnaise.
Cut the herring fillet into pieces.
Place a piece of herring at the bottom of each roll. Put about one teaspoon of beets on top.
Lay one more piece of herring on top and garnish with a sprig of dill. Put on a platter with lettuce and serve.
Bon appetit and Happy New Year!