Prepare the rice in salted water according to the instructions on the packet. Remove the outer leaves and the stalk from the pointed cabbage. Blanch the cabbage in salted water and drain.
Separate eight large leaves, cut out the hard roots and always place 2 leaves on top of each other. Cut about 100 g of the remaining cabbage into fine strips.
Grate the carrot, cut the onion and cucumber into fine cubes. Peel and dice the tomato. The tomato is easier to peel if you scald it with hot water beforehand.
Steam the onion cubes in a little oil until translucent. Add the cabbage strips and grated carrots and cook for about 5 minutes. Mix in rice, cucumber, tomato, herbs and mustard. Season to taste with salt and pepper.
Spread the mixture on the prepared cabbage leaves, then roll them up and tie with kitchen twine. Fry the roulades well all over in a little oil. Add the vegetable stock and stew for about 20 minutes.