In a small bowl, mix together the garlic powder, Italian seasoning, dried mustard, and onion powder. Rub the spice mixture all over the pork butt.
In a large skillet over medium-high heat, melt the butter. Add the pork butt to the skillet and cook until browned on all sides, about 5 minutes per side.
Transfer the pork butt to a slow cooker. Pour the chicken broth (or veggie broth) over the pork butt. Sprinkle with salt and pepper.
Cover the slow cooker and cook on low for 7 hours, or until the pork is tender and falling apart.
Remove the pork butt from the slow cooker and let it rest for a few minutes. Use two forks to shred the pork.
Serve the shredded pork with the cooking juices from the slow cooker. Garnish with freshly chopped parsley, if desired.
