Slice the chicken teriyaki into thin strips.
Take a slice of bread and spread about a tablespoonful of honey-mustard sauce over the entire surface.
Cover the bread with shredded lettuce.
Arrange the chicken teriyaki strips on top of the lettuce.
Pile on the mushrooms slices on top of the chicken.
Top the mushrooms with onion rings.
Cover with another slice of bread.
Repeat to make another sandwich.
Slice the sandwiches into triangles (or not) and serve.