Soak the buns. Peel the carrot and cut into long, thin slices with a peeler. Peel and chop the onion. Knead minced meat, egg, squeezed out roll and onion.
Season with salt and pepper. Roll out on foil to a plate of about 35x20 cm. Cover with cheese and carrot slices and form into a firm roll with the help of the foil. Place on a baking tray coated with oil.
Cook in the preheated oven (electric cooker: 175 °C/ gas: level 2) for 40-45 minutes. In the meantime, remove outer savoy cabbage leaves if necessary. Quarter the savoy cabbage and cut off the stalk. Cut cabbage into fine strips.
Heat the fat. Sauté the savoy cabbage for about 10 minutes. Season with salt and pepper. Deglaze with 1/4 litre water. Cover and cook for another 10 minutes. Stir in crème fraiche and season to taste again.
Arrange the sliced cheese roll on the savoy cabbage. Serve garnished with fresh herbs.