Prepare the ribs by removing the membrane and trimming them down to fit in your smoker, if needed.
Coat ribs with yellow mustard, then combine dry rub ingredients and thoroughly coat all sides of the ribs.
Place the ribs into your preheated smoker and smoke at 225°F for three hours.
Wrap the ribs in foil with butter and brown sugar. Place the brown sugar and butter in the foil first then lay ribs meat side down in the foil. Wrap foil and seal well.
Place ribs back in the smoker and cook at 225°F for another two hours.
Remove the ribs from the foil and carefully place them back onto the smoker and smoker for one last hour at 225°F.
Remove the ribs from the smoker and allow them to rest for 20 minutes. Then serve.