Prepare the Mushrooms:

1. Preheat the Oven: Preheat your oven to 400°F (200°C).
2. Clean and Slice Mushrooms: Gently wipe the mushrooms with a damp cloth to clean them. Remove the stems if necessary, and slice or halve the mushrooms into bite-sized pieces.

Make the Marinade:

3. Combine the Ingredients: In a bowl, whisk together the olive oil, balsamic vinegar, soy sauce, minced garlic, thyme (if using), and brown sugar or honey (if using). Add a pinch of salt and pepper to taste.
4. Toss the Mushrooms: Place the mushrooms in a large bowl or Ziploc bag and pour the marinade over them. Toss gently to coat all the mushrooms evenly.

Roast the Mushrooms:

5. Arrange on a Baking Sheet: Spread the mushrooms in a single layer on a baking sheet lined with parchment paper or a silicone mat for easy cleanup.
6. Roast in the Oven: Place the baking sheet in the oven and roast the mushrooms for 20-25 minutes, stirring halfway through to ensure even cooking. Roast until the mushrooms are golden brown and have released their juices.

Serve:

7. Garnish and Serve: Once roasted, remove the mushrooms from the oven and garnish with freshly chopped parsley. Serve immediately as a side dish or use as a topping for meats, pasta, or salads.