Portobello and Leek Rollups

4 to 6 tablespoons olive oil
8 leeks, chopped
6 ounces portobello mushrooms, sliced or chopped
1 pound bok choy, finely chopped
3 cups shredded mozzarella cheese
4 tablespoons Italian dressing
8 to 10 large flour tortillas

Preheat oven to 350 degrees F.

Heat olive oil in heavy skillet. Add leeks, portobellos, and bok choy; saut