For the rump steak with onion-mustard crust, peel the onion, finely dice it. Peel the carrots and kohlrabi, clean the spring onion and cut everything together into coarse sticks.
Clean potatoes and cut into small wedges. Season the rump steaks with salt and pepper, coat well with mustard, place on top of the onion cubes, press on well, then press on some flour.
Put the rump steaks in a frying pan with hot fat, and sear hot, turn to the other side, fry at a moderate temperature until pink to the point.
Fry potatoes in hot clarified butter until golden, season with salt and pepper. Saute remaining onions in hot oil until translucent. Add spring onions, carrots and kohlrabi, pour in veal stock, season with salt and pepper, reduce slightly.
Arrange rump steak with onion-mustard crust, potatoes and root vegetables, drape stock over and garnish with marjoram.