Place roast in slow cooker. Mix remaining beef ingredients in a bowl then pour over meat. Cook on low for 8 hours or on high for 4-5. Remove meat and shred, discarding any extra fat. Return to liquid and mix. Keep warm.
Melt butter in a large mixing bowl. Add sugar and mix well. Add eggs and buttermilk then whisk until blended. Add baking soda, cornmeal, flour and salt. Mix until well blended and no lumps remain. Fold in chilies, cheese, and onion. Cook in waffle iron until brown and slightly crisp.
Serve BBQ beef over waffles. Add extra cheese and onions if desired.