Add rice to boiling stock, bring to the boil, cover and allow to swell over a low heat for about 20 minutes. Meanwhile peel and finely dice the onion. Peel and finely chop the garlic.
Carefully remove 12 of the outer leaves of the Chinese cabbage from the head and wash them carefully (should not break, use the remaining cabbage for other purposes). Place in a large pot of boiling salted water and blanch for 1-2 minutes.
Then carefully lift it out with a skimmer and let it drip off on kitchen paper. If necessary, cut ribs flat with a knife. Heat 1 tablespoon of oil in a pan. Crumble the minced meat into it and fry it thoroughly while turning.
Add half of the onion and garlic, fry briefly. Season with salt and pepper. Add rice and parsley and mix in. Remove from the heat and set aside. Place the Chinese cabbage leaves next to each other on a work surface.
Spread the chopped-rice mixture evenly on top, leaving an approx. 1 cm wide edge on each leaf. Fold down the edges and roll up into 12 roulades. Stick together with wooden skewers. Clean, wash and halve the tomatoes.
Heat 1 tablespoon of oil in a frying pan and sauté the remaining onion and garlic. Add the tomatoes and fry briefly. Add tomato paste, sauté briefly and deglaze with chunky tomatoes.
Bring to the boil, season with salt, pepper, paprika and sugar. Divide the sauce into four ovenproof dishes (1 per person) or a large casserole dish. Put the cabbage rolls in it, sprinkle with cheese.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 18-20 minutes. Remove from the oven and serve sprinkled with thyme.