Freeze the cabbage 3 days before you need it. The night before defrost cabbage and keep it in the fridge until you are ready.
Cook rice in plenty water the same way you would pasta until al dente, it shouldn't be too soft- about 5 minutes. Drain and set aside.
In a frying pan heat olive oil and cook onions over low heat for 7-10 minutes until tender.
In a large bowl combine beef, pork, parsley, onions, carrots, rice, salt and pepper.
In a medium bowl whisk together stock, crushed tomatoes and creme fraiche. Set aside.
Place your head of cabbage on a cutting board, cut off the bottom and pull the leaves away from the stalk. Repeat with the second head of cabbage.
Preheat your oven to 350F/180C.
Clear your work space, so all ingredients are within reach. Take a cabbage leaf and put 2 tbsp. of filling at the bottom of the wide part of a leaf (see picture above) and roll it like a burrito, tucking sides in. Your cabbage rolls will vary in size slightly depending on the size of cabbage leaves. You will have approximately 30-32 cabbage rolls.
Pour a cup of the sauce on the bottom of your cast iron casserole or any other heavy bottom casserole and start stacking your cabbage rolls. Half way through add a couple of bay leaves and continue stacking until all cabbage rolls are gone.
Pour the sauce over cabbage rolls, cover with a lid and bake in the oven for 1 hour.
Then take the lid off and bake for 30 more minutes.
Serve with additional sour cream or creme fraiche.