Form to roll (if someone has, I did on a normal cookie sheet) lay out parchment paper, lightly grease it with oil. Pre-heat the oven to 190 degrees Beet to clear, cut with a mixer and grind into a puree. Add cumin, butter, onions and egg yolks. Season with salt and pepper. Mix well. Ready beet puree to shift into a large bowl.

Egg whites whipped in a lush foam. Gently introduce them to the beet puree.

Beet transfer the mixture to a layer in the form of rolls and bake in the oven for 15 minutes.

The mash is ready when you touch it feels thick and slightly hardened. On a wire tray (I use the grill from the oven) spread a clean kitchen towel. Turning the form, carefully dump the beet layer on a towel and remove the parchment paper slowly, tearing it into thin strips. I was able to remove it entirely, but here really need to act very carefully so as not to damage the baked "masterpiece" :)

Now prepare the filling for rolls. Sour cream or cream (need to get fat to make them hard to beat, otherwise the filling will be liquid and may leak out of the roll) to beat in a fairly lush foam, then add the vinegar, mustard, sugar, parsley, dill and horseradish. Mix well. Shift this mixture to the beet layer. Roll up the roulade, lifting the towel over the edge, and allow to cool to room temperature. That's all.