Wash the potatoes thoroughly, cover and cook in plenty of water for about 20 minutes. Peel and finely dice the onions. Clean, quarter and wash the savoy cabbage. Cut savoy cabbage into fine strips.
Heat 30 g butter in a pot and sauté half of the onions in it. Add savoy cabbage, braise briefly and season with salt, pepper and nutmeg. Add 1/8 litre water and simmer covered for about 10 minutes.
Chop the gherkin. Mix the remaining onions, cucumber and mustard. Spread the roast beef slices thinly with the mixture, roll them up and wrap each with 1 slice of bacon. Drain potatoes, rinse with cold water and peel.
Heat the oil in a frying pan or casserole and fry the roulades briefly and thoroughly, turning them over. Season with a little salt and pepper and deglaze with 200 ml water. Add brandy and cream, bring to the boil and braise covered for about 5 minutes.
Heat 30 g butter in a pan and fry the potatoes until golden brown, turning them over. Wash the thyme, dab dry and remove the leaves. Finally add the thyme to the potatoes and season with salt and pepper.
Stir the sauce thickener into the roulade stock, bring to the boil again briefly and season to taste with salt and pepper. Heat the savoy cabbage again and arrange on a plate with the roulades. Add the roast potatoes separately.