Territorial Casserole

1 1/4 pounds lean ground beef, crumbled
1/2 cup chopped onion
3 tablespoons dry taco seasoning mix
1 (14 1/2 ounce) can Mexican-style tomatoes
    (discard 2 tablespoons liquid)
2 (15 ounce) cans pinto beans
1/3 cup ripe olives, sliced
3 tablespoons chopped fresh parsley
4 ounces shredded Monterey jack cheese
1 can refrigerated cornbread twists
1 egg yolk, slightly beaten
1 tablespoon water

Saut