In the same skillet, add the white wine or chicken broth and 1 tablespoon of butter over medium-high heat. Use a wooden spoon to scrape the browned bits from the bottom of the pan. When the butter melts, add the mushrooms and onion; sauté until soft, about 5-7 minutes. Add the garlic and cook, stirring constantly, for 1 more minute. Stir in the soup and milk; bring to a gentle boil. Reduce the heat to low; simmer, stirring regularly, for about 5 minutes. Add extra milk to thin the sauce, if desired, until it reaches your desired consistency. Remove from heat; stir in the parsley and lemon juice. Taste and season with salt and pepper, if necessary.