Instructions:
- Gently wipe the mushroom caps clean; do not rinse under water. Carefully snap off and discard the stems. Use a small spoon to gently scrape out the dark gills on the underside.
- In a small bowl, whisk together the olive oil, 30ml balsamic vinegar, minced garlic, oregano, thyme, salt, and pepper to create the marinade.
- Place the cleaned mushroom caps (gills up) in a shallow dish or zip-top bag. Pour the marinade over, ensuring both sides are coated. Let them marinate at room temperature for at least 30 minutes.
- While marinating, make the glaze: Combine the 240ml balsamic vinegar and brown sugar in a small heavy-bottomed saucepan. Bring to a simmer over medium heat, then reduce heat to low and let it bubble gently for 10–15 minutes, stirring occasionally, until it reduces by half and coats the back of a spoon. Set aside to cool slightly.
- Preheat your grill or grill pan to a medium-high heat (around 400°F / 200°C). Lightly oil the grates.
- Place the mushrooms gill-side down on the hot grill. Grill for 4–5 minutes until distinct grill marks appear.
- Flip the mushrooms over (cap-side down). Baste the cooked side generously with the reserved balsamic glaze. Cook for another 4–5 minutes until the mushroom is tender when pierced with a fork.
- Remove from the grill, allow to rest for two minutes, and drizzle with any remaining glaze just before serving.