Carefully remove the stalks from the mushrooms and discard. Use a teaspoon to scoop out the mushroom gills. Brush the mushrooms with half a tablespoon of olive oil and arrange on a shallow oven tray. Bake for 10 minutes until tender and drain off any excess liquid.
Step 3
Whilst the mushrooms are cooking, finely dice the tomatoes, discarding the seeds and crush the garlic. Add to a mixing bowl with the salt and pepper, remaining olive oil and balsamic vinegar. Stir well to combine.
Step 4
Once the mushrooms are cooked, divide the tomato mixture evenly between the two, filling the center.
Step 5
Transfer back to the oven for a further 8 minutes until the mushrooms and tomatoes are tender. Finely chop the basil and scatter over the top to serve.