In Auckland there is a café and deli called Zarbo, and they put out this wonderful cookbook that Mum gave Mark a copy of a few years ago (We had a Zarbo carrot cake at our wedding). This recipe is form their book, and I see they have a new book coming out soon.
12 Large Portobello mushrooms
2 cloves garlic; finely diced
2 tablespoons balsamic vinegar
4 sage leaves; sliced
1 large sprig rosemary, leaves pulled from the stalk
1/2 cup olive oil
sea salt flakes
set oven to 160°C. Lay mushrooms on a baking tray. Mix together garlic, vinegar, sage, rosemary and oil, and brush over the mushrooms. Place sprigs of thyme on top and sprinkle with sea salt. Bake for 20 minutes.