I've made this using seasoned black beans instead of the TVP. Yummy! I like to add shredded cabbage to the lettuce and I often skip the tortillas (mostly because I don't keep them on hand!)
Penny - TVP is textured vegetable protein, i.e. a vegetarian hamburger. You buy it dry in a box and reconstitute it. I've ordered some called Beef Not that's good. Can't recall the website, but you could google it. The Yves ground round is a frozen soy product, substitute for hamburger.
"Promise me you'll always remember: You're braver than you believe, and stronger than you seem, and smarter than you think." Christopher Robin to Pooh