Mix some beef mince, sumac, finely diced onion, cooked rice, and chilli flakes. Wrap the mixture in the leaves from your mini cabbage.
Pop the parcels in a single layer in your slow cooker.
Mix passata, 4 teaspoons of brown sugar, a cup of chicken stock and some thyme and pour over your cabbage rolls. Cook on low for about 4 hours or until the cabbage is tender and the mince cooked. You may need to do the last half hour with the lid off to reduce the sauce to a sticky consistency (depending upon your slow cooker model)