Giant garlic mushroom burgers

1. Preheat oven to 200°C/180°C fan/gas mark 6. Put onion, half of the garlic, 2 teaspoons of oil, the balsamic vinegar and black pepper in a small, non-stick roasting tin; toss to mix well. Spread out in a single layer; nestle mushrooms, stem-side up, in amongst onion mixture. Combine remaining garlic and oil; brush tops of mushrooms with garlic oil mixture. Bake in oven for 15–20 minutes or until vegetables are softened and onions are just starting to caramelize.
2. Remove from oven; combine cheese, parsley and chives. Sprinkle herby cheese on top of mushrooms. Return to oven; bake for about 5 minutes or until cheese is melted.
3. Fill each bread roll with some roasted onion mixture, topped with two cheesy mushrooms (remember to drizzle over any delicious cooking juices, too). Add a tomato slice to each roll, if you like. Serve with remaining tomato slices and a mixed green leaf salad alongside (if using).

Cook's tips

• Edam or Gouda cheese can be used in place of Cheddar-style cheese, if you prefer.
• Why not have a lighter version by serving each halved roll as an open sandwich?
• Simply top each roll half with some onions and a mushroom.
• Use very fresh, crusty rolls. Alternatively, rolls can be halved and lightly toasted or griddled before filling.