Saute onion, celery and peppers in olive oil and butter about 10 minutes until soft. Stir in corn.
Mash beans with taco seasoning and divide mixture, spreading about 1 1/2 Tablespoons in the bottom of each taco shell.
Top beans with 1/2 thin slice of pepper jack cheese, sauteed vegetables, then chicken and finally grated cheddar. Can be covered and refrigerated at this point for baking later.
Bake at 350 degrees for 15-20 minutes until hot and melty. If dish has been refrigerated, baking time may be slightly longer.
Top with shredded lettuce, diced tomato, avocado and/or a dollop of sour cream if desired