To make the tomato sauce: Add oil, garlic, and salt to a medium-high heat pan and sweat for 1-2 mins. Add carrot and celery and sweat for another 4 mins. Add tomato paste, bay leaf, thyme, and parsley and further cook for 1-2 mins. Pour in tomatoes, fill can halfway with water and add to sauce. Cook for a further 20 mins half-covered with lid.
To make cabbage roll filling: Preheat oven to 200°C. Mix together onion, rice, garlic, parsley, mince and season with salt and pepper. Carefully remove cabbage leaves and boil for 1 minute in water with a good amount of salt. Chill in an ice bath before patting dry.
To assemble the cabbage rolls: Fill each cabbage leaf with 65g-70g of filling. Spread tomato paste in a roasting pan and place cabbage rolls on top. Roast for 15-20 mins until slightly charred and piping hot.