Place onion, garlic, mushrooms, and butter in a small microwaveable casserole. Place a microwave-friendly cover on top.
Cook on high for 3 to 4 minutes or until the mushrooms are tender. Drain and set aside.
Trim fat from steak. Slice the steak against the grain into thin strips.
Place the chicken strips in a medium microwaveable casserole and stir in the Worcestershire sauce. Place microwave-friendly cover on top. Cook on medium, stirring twice in between, for 7 to 8 minutes or until the meat is no longer pink.
Mix corn flour and water. Add to meat and mix well. Stir in cooked vegetables, paprika, salt, and pepper.
Cover and cook on medium for 9 to 11 minutes or until the chicken is tender. Stir in the sour cream.
Cover and cook on medium again for 2 to 3 minutes or just until thoroughly heated.