How much to cook barley for stuffed cabbage?

Cabbage rolls with barley

Products
Cabbage - 1 head of cabbage about 2 kilograms
Beef and pork - 150 grams each
Pearl barley - 90 grams (half a glass)
Bow (large) - 1 head
Carrots - 1 piece
Garlic - 4 cloves
Parsley - 1 bunch
Sour cream 20% fat - 2 tablespoons
Ketchup or tomato paste - 2 tablespoons
Vegetable oil - 1 tablespoon
Wheat flour - 1 tablespoon
Ground black pepper - 0.5 teaspoon
Table salt - half a teaspoon

Food preparation
1. Rinse 300 grams of meat and mince.
2. Rinse 90 grams of barley under running water in a colander, pour 1.5 glasses of water and cook until half cooked for 50 minutes (with preliminary soaking of barley for 2-3 hours, the cooking time will be about half an hour). Cool the boiled cereal a little.
3. Peel the onion and chop finely. Scrape the carrots with a knife and grate on a coarse grater.
4. Put onions with carrots in a frying pan preheated with vegetable oil and fry for 5 minutes.
5. Peel 4 cloves of garlic, rinse the bunch of parsley and chop everything.
6. Make minced pork and beef using a meat grinder.
7. Stir the minced meat, fried vegetables, barley, parsley, chopped garlic, add 0.5 teaspoon of ground black pepper and a teaspoon of table salt.
7. Mix in a separate bowl 2 tablespoons of ketchup or tomato paste, the same amount of sour cream of 20% fat and a tablespoon of wheat flour. Add 200 milliliters of water, salt to the sauce and again mix.
8. Wash the cabbage forks and disassemble into sheets. Remove damaged and heavily soiled (as a rule, the top sheets), and put the rest in boiling salted water for 6 minutes.
9. Cool the boiled leaves slightly and cut off the thick veins at the base. Then to the center of each sheet, put 2 tablespoons of the filling and wrap in the form of an envelope.