In a large skillet, cook the bacon until crispy, then remove it from the pan and set aside.Cook the onion in the bacon fat until soft. Add the garlic and thyme, and sauté for an additional 1-2 minutes.Add the flour, stir and brown for several minutes, then add in 2 cups broth and gently stir until thickened.Add this thickened gravy mixture to the slow cooker, along with the potatoes and rest of the broth.Cook 5-6 hours on low, or until the potatoes are soft.minutes before serving, add 1.5 cups cheese, the sour cream, and the heavy cream to the slow cooker. Using a potato masher or immersion blender, mash the potato chunks to make a smoother consistency. (I still like to leave some chunks in there, though)Heat through, then serve. Top with bacon bits, the remaining cheese, and chives, if desired.