Stuffed mushrooms

2 large, flat field mushrooms

2 tablespoons olive oil, plus extra for brushing

2 spring onions, chopped

½ red pepper, cored, deseeded and chopped

1 small courgette, chopped

4 pitted olives, chopped

2 tablespoons porridge oats

1 tablespoon chopped basil

1 tablespoon soy sauce

1 tablespoon lime juice

salt and pepper