1. Heat the oil in a large skillet over medium to medium-high heat. Season the meat, and the bone, if using, with salt and pepper, and brown thoroughly. Remove the meat and bone from the pan and add to the crock of the slow cooker.
2. Add the tomato paste to the skillet and stir into the pan drippings to soften. Add the wine to deglaze the pan, stirring the wine and tomato paste together. Pour the mixture over the meat, then add the rest of the ingredients except the pumpkin. Cook for 6-8 hours on high or 8-10 hours on low.
3. Before serving, remove about 1/2 cup each of the broth and some of the potatoes, carrots, and onions. Add them to the base of a blender or a bowl and use an immersion blender. Blend the broth and vegetables. Add the pumpkin to the puree and blend again until combined; add more broth if needed. Transfer the vegetable puree to the crockpot and stir to combine. Cover and re-warm, about 20 min. Remove the bone and bay leaf and serve immediately.