1 small onion, chopped
1 Tbsp. olive oil
2 (8-oz) pkgs. sliced mushrooms
2 cups boneless, skinless chicken breasts, cut into cubes
3 Tbsp. all-purpose flour
1½ cups fat-free-milk
1 (16-oz) package steam-in-bag broccoli florets
1 (5.3-oz) container fat-free plain Greek yogurt
¼ cup light mayonnaise
¼ tsp salt
¼ tsp. pepper
¾ cup Mexican style cheese blend