Preheat oven to broil on low
On stovetop, heat oil in skillet to medium high
Saute chicken breasts, peppers onions and mushrooms until vegetables are softened and start to carmelize (3-5 min).
Remove veggies and set aside.
Flip chicken and cook until internal temp is 160-165.
Remove chicken from pan and slice to thick slices.
Add chicken and veggies back to pan and add 1/4 cup teriyaki sauce. Stir until sauce is evaporated and all items are heavily coated.
Line a cookie sheet with parchment paper and lightly spray with non-stick spray
Open sub roll and lay on parchment
Top both sides of sub roll with chicken & veggies
Top with Swiss cheese
Broil for 2-3 minutes until cheese starts to bubble and brown SLIGHTLY. (This time can vary greatly according to your broiler. Start with broiler on low and watch it closely – you just want the cheese to melt.)
Remove from oven
Fold over subs and serve!