Beforehand, prepare the cabbage by either freezing it for a week and then thawing it or steaming it until it's loose but sturdy and allowing it to cool.

When it is room temperature, core the cabbage. Set it aside for later.

Put the ground meat in the large bowl. Sauté the diced onion in about 2 tablespoons of oil, saving the remaining oil in the skillet for later.

Remove the onions when they are translucent and add them to the meat.

Next, add the sour cream, mustard powder, 3/4 cup of chopped parsley, 1 teaspoon cayenne pepper, 1 tablespoon salt, 1 teaspoon paprika, 1 teaspoon black pepper, 1 teaspoon thyme, 1 teaspoon marjoram, and 1 cup of uncooked rice. Mix together by hand until all the ingredients are fully combined — you should feel an even distribution throughout the meat.

Add about 5 inches (12 cm) of water to the stockpot. Pull a leaf from the cabbage head and place it in your hand, spine-side facing you, with the base of the leaf at the heel of your hand. Starting from the narrow inner end of the spine, shave off enough of the raised rib to make the leaf an even thickness — this makes rolling much easier. Flip the leaf over so the spine rests in your palm and the outer edge faces your fingertips, cupping your hand to follow the leaf's natural curve.

Place about 2-3 tablespoons of filling in the cupped leaf, roughly shaped into a short log, about an inch (2.5 cm) up from the bottom edge. Roll from the base toward the tip of the leaf, tucking the sides in as you go to enclose the filling completely. Place each finished roll seam-side down in the stockpot. When you reach the small inner leaves that are too small to roll, tear them up and scatter them into the pot. Shape any leftover filling into small meatballs and add them as well. Crush the 16 ounces (450g) of cooked, peeled tomatoes by hand and add them to the pot.

Add enough water to cover the rolls, and sprinkle on top some thyme, marjoram, chopped parsley and 1 bay leaf. Use your judgement on seasoning — you can always put it in, but you can't take it out again.

In the skillet, brown about 1/4 cup of flour in the leftover oil. When it is brown and lumpy, thin it to smoothness with water and add a dash each of paprika, salt, pepper, marjoram, thyme, and then thin down to smoothness again. This is a roux designed to thicken the liquid in the pot.

Add the roux to the pot and ensure all rolls are submerged in liquid — add more water if needed. Cover, bring to a boil over medium heat, then immediately reduce to a low simmer. Cook for 2 to 2 1/2 hours, until the cabbage is completely tender and the rice inside the rolls is cooked through. The liquid should barely bubble — a hard boil will toughen the leaves.

In the last 10 minutes of cooking, stir in the 2 cups (480ml) of tomato passata and let it heat through. Taste the broth and adjust seasoning if needed. Discard the bay leaf before serving.