Begin by rinsing 1 pound of baby bella mushrooms under cold water to remove any dirt. In a large pot, add these mushrooms and cover them completely with water. Place the pot on the stovetop and bring the water to a boil over high heat, watching for the rapid bubbling that indicates it's time for the next step.

Once boiling, carefully pour in ½ cup of white wine vinegar, stirring gently. Reduce the heat to medium and remove the pot's lid. Allow the mixture to simmer for 5 minutes; you’ll notice the mushrooms starting to soften and become a shade darker.

After 5 minutes, remove the pot from heat and drain the mushrooms thoroughly using a colander. Give them a gentle shake to get rid of excess water.

In a small bowl, combine ½ cup olive oil, 3 minced garlic cloves, 2 tablespoons chopped fresh parsley, and 1 small minced shallot. Add in 2 teaspoons of chopped fresh lemon thyme, 1 teaspoon of dried oregano, and season with salt and ground pepper to taste. Mix these ingredients until well blended.

Transfer the warm, drained mushrooms into a large mason jar. Pour the marinade mixture over the mushrooms, ensuring every piece is covered beautifully. Seal the jar with its lid tightly, then shake it gently to coat the mushrooms thoroughly.

Let the sealed jar of marinated mushrooms cool down to room temperature for about 30 minutes. Once cooled, place the jar in the refrigerator, where it can marinate further.

After at least an hour in the fridge—or preferably overnight—the marinated mushrooms are ready to serve! They can stay fresh for up to a week in the refrigerator.