Preheat oven 220ºC. Combine the olive oil, balsamic vinegar, garlic, brown sugar, sweet chilli sauce and salt and pepper in a screw-top jar, shake well to combine. Place mushrooms into a large bowl and pour over the vinegar mixture. Toss well to combine.
Spoon the mushrooms and marinade into a greased baking dish and roast for 20-25 minutes, tossing twice during cooking, or until tender. Sprinkle with herbs and serve. Great accompaniment to roast or grilled meat and chicken.