Clean and wash well, but do not skin them. Put in a crockery vessel a layer of rye straw, moisten it slightly, place the beets on it, cover the vessel, and place it in a slow oven for five or six hours; cool and skin them. When cooked, cut them in thin slices. Put butter in a stewpan, and when melted sprinkle in it a pinch of flour, a teaspoonful of chopped parsley, salt, and pepper, then the beets; simmer twenty minutes, add a few drops of vinegar, and serve.