Warm a large skillet over medium high heat and cook the bacon until the fat has rendered and the bacon is crispy. Remove the bacon, and set aside 2 tbs drippings, leaving the rest in the pan.
Pat the beef cubes dry and sprinkle with salt and pepper. Sear the beef cubes in the bacon fat in a single layer, working in batches if necessary. Remove the seared beef to the bowl of a slow cooker.
Cook the carrots and onion in the skillet about 10-15 minutes, waiting for the carrots to soften and the onion to slightly caramelize. Add the garlic and tomato paste, cooking for 1-2 minutes more. Transfer the vegetables to the slow cooker with the beef.
Add the thyme and bay leaf to the slow cooker along with 1 1/2 cup of the wine and broth. There should be enough liquid to almost cover everything, about 3/4 of the way. Cover the slow cooker and cook on low for 6 to 8 hours, until the beef is fork tender.
Meanwhile, deglaze the skillet with the remaining 1/2 cup wine and let that cook down. Add the remaining 2 tbs bacon fat and mushrooms, then cook until they have released their liquid and that has evaporated
Meanwhile, add the remaining 2 tbs bacon fat to the skillet and add the mushrooms. Cook until they have released their liquid and add the remaining wine. Cook until the liquid has evaporated and the mushrooms are golden brown. Add these mushrooms to the crispy bacon that was set aside earlier.
Once the beef has cooked, stir in the reserved bacon and mushrooms, then cook on high or simmer until the mushrooms are warmed through, about 10 minutes.
Serve alongside mashed potatoes or a crusty piece of bread, sprinkle with parsley if desired.