Clean the mushrooms gently with a damp cloth and trim the stems if needed. I like leaving them whole for a meatier texture.
In a large mixing bowl, combine olive oil, balsamic vinegar, soy sauce, chopped garlic, thyme, salt, and pepper. Whisk briefly so everything blends.
Add the mushrooms to the bowl and toss until every mushroom is coated evenly. I make sure each one has a little bit of the balsamic-soy mixture clinging to it.
Spread mushrooms in a single layer on a baking sheet. Roast in the oven for about 20 minutes, stirring halfway through for even browning.
Once tender and caramelized, remove from the oven and serve immediately. I sometimes sprinkle extra thyme on top for a fresh, aromatic finish.