Heat the olive oil and butter or margarine in a large skillet over medium heat. Add the garlic and onion, season with salt & pepper to taste. Cook for 5 minutes.
Add the chicken to the skillet, pushing the onions and garlic to the side of the skillet. Brown for about 6 minutes on each side, or stir and flip for about 10 minutes total for cubed chicken. Be careful not to let the onions or garlic burn. Once fully cooked, remove chicken to a plate and set aside.
Add the mushrooms to the skillet and continue cooking for about 5 minutes, or until the mushrooms are fully cooked. Stir 3 T. flour into the skillet. Whisk in chicken stock and milk. Bring to a slow boil and boil until thickened to gravy consistency. Stir in sour cream, thyme, and salt & pepper to taste.
If you’re cooking this meal stolen moments style, let cool and place in a serving dish, plastic container, or keep in the skillet in the refrigerator. To reheat, warm on the stove, in the oven or in the microwave. Serve alongside or on top of brown rice pilaf.