Preheat oven to 350; spray/grease a 13x9 pan, set aside.
Cook chicken breasts in water in a saucepan (I usually add some cooking sherry) OR use leftover grilled/roasted chicken meat. Cut into bite-size pieces; set aside.
While chicken is cooking, prepare ravioli according to pkg instructions--but leave them a bit firm as they continue cooking in the oven; drain, rinse and place ONE LAYER in prepped pan.
In a separate bowl, mix alfredo sauce, chicken pieces (if used) & drained mushrooms; pour HALF over the pasta in the pan. **I also added enough water to swish out the alfredo jar--probably about a half cup?--to be a bit juicier sauce.**
Sprinkle with about 1/3 of the cheese; add remaining pasta in a layer, cover with remaining sauce-chicken-mushroom mixture.
FINISH with remaining cheese.
Bake for 30-45 minutes until bubbly. Serve immediately.
ALTERNATIVE: Add coarsely chopped & sauteed onion to kick up the flavor buds!