In a large skillet, heat 1 tablespoon olive oil over medium-high heat. Add chicken strips, making sure not to overcrowd the pan. You may need to cook in batches, adding more oil as needed.
Brown chicken, turning after 2-3 minutes on each side. Remove from pan and place in a 9x13" casserole dish.
Using the same skillet, heat ½ tablespoon olive oil. Add onions and cook over medium heat until soft. Add cream cheese and stir until melted.
To the cream cheese, whisk in condensed soup, milk and garlic powder. Stir in drained mushrooms. Season with additional salt or pepper to taste.
Pour sauce over chicken. Cover with foil and bake for 35-45 minutes or until chicken is cooked through and sauce is bubbly.
Serve alone, or over rice or egg noodles.
Video
Notes
*Replace frozen onion with one small diced onion.To use fresh mushrooms in place of canned mushrooms:
Heat 1 tablespoon of oil in a large skillet over medium heat. Add 1 1/2 pounds of sliced fresh mushrooms in a single layer. Cook for 3-5 minutes without stirring until browned. Toss, and cook for an additional 3-5 minutes.