Remove the tough outer layer of leaves from the cabbage
Put the cabbage core side down in a large microwave-safe bowl and add ½ cup of water
Microwave on high for 10 minutes
Carefully turn the cabbage and microwave for a further 10 minutes
When the cabbage is cool enough to handle, cut around the base to loosen leaves, peeling them off the head.
When you have 16 softened cabbage leaves of roughly the same size, set them aside while you make the filling.
In a bowl, combine egg, ground beef, rice onion, oregano, thyme, salt, and pepper.
In another bowl, combine tomato sauce, tomato paste, Worcestershire sauce, and brown sugar.
Cover the bottom of the slow cooker with any excess cabbage leaves
Pour ½ of the sauce over the leaves in the slow cooker
To make the rolls, put a ¼ cup of filling down the center of each cabbage leaf.
Fold up the sides and then roll the leaves, placing each roll seam side down in the slow cooker, until you have one layer.
Cover with the remaining tomato sauce mixture.
Pour the remaining sauce over the top.
Cover and cook on low 6-8 hours
Make ahead: You can make the cabbage rolls the day before, keep them in the fridge overnight and transfer them to the slow cooker in the morning.Leftovers: These cabbage rolls will keep in the fridge for 2-3 days and can be reheated in the microwaveOf course, the cooking time here is passive because we're slow cooking, but all slow cookers are different, so cook time can vary depending on your cooker.Use the remainder of your cabbage in soups or stews, and you can save the cabbage cooking water for soup, too.This recipe is gluten-free if you use a gluten-free Worcestershire sauce