Bring enough water to cover the beef brisket to a boil in a large pot. Add the 1 kg beef brisket and skim off any foam that rises to the surface.
Add the 2 chopped onions, the 1 bunch soup greens (roughly chopped), salt, pepper, 3 carnations, and 2 bay leaves. Reduce heat to medium-low and simmer for 2 hours.
Remove the beef brisket from the pot and portion it into serving pieces.
Arrange the meat portions on a serving plate, pour some of the hot cooking broth over it, and serve with horseradish sauce, boiled potatoes, and pickles.