Cut beef (or moose or venison) into 1" or 2" chunks and place in dutch oven (no oil is needed). Cook on medium heat until meat releases juices. Add frozen chopped green chile or fresh roasted, peeled and chopped chile and garlic. I actually prefer to use garlic granules if you have it. Don't even try to use canned chile because it is preserved with vinegar which will impart a nasty taste. Add red chile flakes (or omit if you don't like a little bite). Add salt and pepper, to taste. Simmer for 4-5 hours or until meat begins to fall apart. You may need to add water to keep it kind of "stewish".
Mix cornstarch with just enough water to make a thickening agent. Add and stir in a small drizzle to thicken.
Serve wrapped in a large flour tortilla with cheese. Top with diced tomatoes, shredded lettuce and sour cream if you like.