Prepare the Mushrooms - Rinse and dry the mushrooms, or wipe the surface with a damp paper towel. Trim the stems and cut them into halves.
Cook the Aromatics - Heat a large saute pan over medium-low heat. Add the olive oil. Once the oil is warm, add the onions. Saute until lightly brown and translucent, about 4 to 6 minutes. Add the minced garlic and thyme, and saute for 30 seconds.
Saute the Mushrooms - Increase the heat to medium. Add the mushrooms, then sprinkle with salt and pepper. Saute until tender, occasionally stirring, about 4 to 5 minutes.
Add the Vinegar and Soy Sauce - Add the balsamic vinegar and soy sauce, stir and cook until most of the liquid evaporates, about 1 to 2 minutes.
Add the Butter - Add the butter and stir to coat the mushrooms. Cook for 1 minute. Season with salt and pepper to taste.
To Serve - Garnish with chopped parsley.
Notes
Recipe Yield: 2 ½ cups
Serving Size: About ⅔ cup
Mushroom Substitutions: Cremini, baby bella, or white button mushrooms.
Make it Gluten-Free: Substitute soy sauce with coconut aminos, Braggs liquid aminos, or gluten-free tamari.
Make it Dairy-Free: Add margarine or plant-based butter.
Storing: Refrigerate for up to 4 days or freeze for up to 9 months.