1 lean boneless beef chuck roast (approx 3lbs to yield 16-18 burritos - sometimes I end up getting two smaller ones to cook in my largest crock) and sprinkle on all sides with 4 tsp chili powder OR Jen's Devilish Delish Seasoning Mix - see post on 11/30/12) and in non-stick pan coated with oil on med-high heat brown meat on all sides to sear seasonings into crust.
Meanwhile in a bowl add & combine:
1 medium onion finely chopped
2 cloves garlic finely chopped/pressed or cheat like me and squeeze from Garden Gourmet Tube
1 small can green chilis diced
1 can rotel tomatoes with green chilis
1 tsp both cumin and chili powder OR 2 tsp of Jen's Devilish Delish Seasoning Mix (see 11/30/12 post)
1 8oz. can tomato sauce (I like using roasted garlic type)
1/4 c. Tequila (optional but good!)
Salt, Pepper and Tabsasco shakes to taste
Place seared beef in crock and cover with sauce from bowl. Cover and cook on low overnight (9-10 hours) til beef is so tender it shreds easily with a fork.
Lift beef from cooker and shred with forks/fingers, discard any fatty bits. Skim any fat on top of cooking liquid. Return shredded beef to cooking liquid. At this point you can serve with warmed tortillas and toppings to suit, i.e. sliced avacado, cilantro, salsa, sour cream, etc. OR if making ahead cool and store in fridge until gameday and begin reheat in crock a couple of hours ahead of serving. A fresh squeeze of lime juice on the meat before serving will wake the flavor right back up!