Partially freeze meat for easier slicing.
Heat oil in a large skillet or wok.
Add steak strips to the oil.
Stir-fry until meat loses its pink color.
Remove meat from pan.
Add additional oil to the pan if needed.
Cook onions and bell pepper until crisp tender.
Return meat to pan.
Add the water, chili powder, cumin, and Worcestershire sauce.
Cook and stir until the water is gone.
Stir in the tomatoes.
Heat through.
Place some of the meat in a warm tortilla leaving the bottom half free.
Top with sour cream, guacamole, and salsa.
Fold sides and bottom in leaving the top open.
