Preheat your smoker to 225°F using oak or hickory wood for an authentic Texas flavor profile.
Trim the beef brisket of excess hard fat, leaving about a quarter-inch of the fat cap to keep the meat moist during the long cook.
Apply a thin, even layer of yellow mustard over the entire surface of the brisket to act as a binder for the spices.
In a small bowl, combine the sea salt, black pepper, garlic powder, and onion powder; sprinkle the mixture generously over all sides of the meat.
Place the brisket in the smoker and cook until the internal temperature reaches 165°F, then wrap it tightly in peach butcher paper to preserve the bark.
Continue smoking the wrapped brisket until the internal temperature reaches 203°F and the meat feels tender like butter when probed.
Remove the brisket from the smoker and let it rest in an insulated cooler for at least one hour before slicing against the grain.
While the meat rests, dice the sweet potato and roast at 400°F for 20 minutes until caramelized.
Steam the green beans until crisp-tender, then toss them with apple cider vinegar and a pinch of salt before serving alongside the sliced brisket and potatoes.