Pat the meat dry and sprinkle generously with salt and pepper.
Melt a generous amount of healthy cooking fat such as lard, ghee or coconut oil in a heavy skillet set over high heat.
Add the meat in a single layer, making sure that the pieces do not touch, and cook until brown on all sides. Work in several batches if you have to so you don’t overcrowd the pan. Remove the cooked pieces of meat to a bowl to collect the juices.
Once all the meat has been cooked and set aside, lower the heat to medium, add a little more fat to the pan if necessary then throw in the onion and garlic and cook, stirring often, until the onion is fragrant and becomes translucent.
Add the broth, red wine vinegar and Dijon Mustard and bring to a simmer. Add the meat and meat juices back to the skillet, stir and kill the heat.
Transfer to slow cooker, add carrots, rutabaga, mushrooms, rosemary and bay leaves
Cook the stew on low for 8 hours or on high for 6 hours.
Once your stew is fully cooked and to your liking, ladle about a cup of the cooking liquid into a small saucepan and bring to the boil.
Meanwhile, in a small container, mix tapioca starch and water together. Pour that into the boiling liquid and cook for a minute, whisking constantly, until thickened.
Transfer this thickened sauce back to the slow cooker and stir until well incorporated.
Serve immediately (don't forget to fish out rosemary sprigs and bay leaves)