Begin by placing your firm and fresh baby Bella mushrooms into a large pot. Pour in enough water to just cover the mushrooms, then add half a cup of white wine vinegar. Cover the pot and heat it over high flames until it reaches a rolling boil—this should take about 3–5 minutes.

Once boiling, remove the lid and allow the mushrooms to cook for 5 minutes. Stir occasionally to ensure even cooking.

After 5 minutes of boiling, take the pot off the heat and carefully drain the mushrooms using a colander. While still hot, transfer them to a clean mason jar.

In a separate mixing bowl, whisk together the olive oil, minced garlic, chopped parsley, minced shallot, lemon thyme, dried oregano, and salt and pepper until well combined.

Pour the prepared marinade over the hot mushrooms in the jar. Seal tightly and gently shake to coat the mushrooms.

Allow the jar to cool to room temperature before refrigerating. Let sit for at least 24 hours for flavors to meld.

After at least 24 hours, your keto marinated mushrooms are ready to serve! Enjoy as a snack or add to various dishes.