Clean, wash and cover the Brussels sprouts and cook them in little boiling salted water for about 20 minutes. Wash the rump steak, dab dry and cut the fat edge several times. Heat 1/2-1 tablespoon of oil in a coated small pan and fry the steak for about 5 minutes, turning it over.
Heat the remaining oil in another pan and fry the croquettes over medium heat until golden brown. Shake the pan several times while doing so. Peel and finely dice the onion. Season the steak with salt and pepper, remove it from the pan and wrap it in aluminium foil.
Braise the onion in hot frying fat. Stir in tomato paste and deglaze with red wine and stock. Add green pepper and simmer covered for 2-3 minutes. Add sauce thickener while stirring and boil up again briefly.
Season to taste with salt and pepper. Drain the Brussels sprouts, add butter and nutmeg and toss in. Arrange steak with pepper sauce, Brussels sprouts and croquettes on a plate. Serve garnished with parsley and pepper panicles.