Preheat the oven to 200C/400F/Gas 6.
For the stuffed pepper, heat the olive oil in a frying pan over a medium heat, add the onion and courgette and fry for 2-3 minutes.
Add the garlic and the chopped pepper half and fry for a further 2-3 minutes.
Add the breadcrumbs and Brie and stir well to combine. Fill the remaining pepper half with the filling mixture.
Place the stuffed pepper on a baking sheet. Transfer to the oven and bake for 15 minutes, or until the pepper is softened and the filling golden-brown.
Meanwhile, for the garlic mushrooms, heat the butter in a small pan, add the mushrooms and garlic and sauté for 3-4 minutes. Stir in the chopped chervil.
To serve, place the garlic mushrooms onto a serving plate, top with the stuffed pepper and drizzle with olive oil.