Cut 2 boneless, skinless chicken breast halves (6 - 8 ounces each) into bite-size pieces. Add to a Medium Ziploc® brand Zip'n Steam® bag.
Seal bag. Pat chicken into a single layer and place bag in microwave.
Cook on full power for 4 minutes (Medium bag) or 3 1/2 minutes (Large bag), until chicken is cooked through, with no trace of pink. If needed, continue microwaving at 30-second intervals until chicken is done. Chicken should be thoroughly cooked before adding remaining ingredients.
Allow bag to stand 1 minute before handling. Carefully open bag. Leave cooked chicken in bag.
Add remaining ingredients to bag with cooked chicken.
Seal bag and gently shake to combine ingredients. Pat ingredients into single layer and place bag in microwave a second time.
Cook on full power for an additional 1 1/2 minutes to melt cheese and form sauce.
Allow bag to stand 1 minute before handling. Wearing an oven mitt, gently squeeze bag to smooth out cheese sauce. If needed, continue microwaving at 30-second intervals until cheese melts and forms a smooth sauce. Carefully open bag and serve.