Process the cabbage. Place the cabbage head in boiling water. The water should cover the vegetable by half. After 2 minutes, turn the cabbage over and boil for another 2 minutes. Remove the head, cool and separate the leaves. If there are any hard ones left, you can boil them separately in the same water for another 2 minutes.
Prepare the filling. Mix the prepared mince with the cooled rice. Add salt and pepper. Mix thoroughly.
Form the cabbage rolls. Step back 1-1.5 cm from the edge of the sheet and put 1 tbsp. of filling. Fold the sheet on three sides, then roll it into an envelope. Do the same with the remaining leaves, using all the filling.
Prepare the sauce. Combine the onion with the grated carrot. Add some sunflower oil to the pan and put the prepared vegetables in. Sauté, stirring constantly, for about 3 minutes. Add the tomato paste and simmer for another 1 minute. Turn off the heat and pour in the sour cream and cabbage leaf broth. Mix thoroughly. Add salt and pepper to taste.
Prepare the cabbage rolls. Add a spoonful of flour to the sauce and stir. Place the cabbage rolls in the sauce. The sauce should almost completely cover the cabbage rolls. If there is not enough volume, add a little cold water. Cover the pan with a lid, reduce the heat after boiling and simmer for 60 minutes.