Put the garlic, rocket and 75 ml (3 fl oz) of the olive oil in a food processor and process to make a thick pesto-like paste. Season with salt and pepper, add 50 g (2 oz) of the breadcrumbs and process lightly to mix.
Arrange the mushrooms in a shallow roasting tin or on a baking sheet. Drizzle with the remaining oil and season with a little salt and pepper. Place on the upper rack of the halogen oven.
Set the temperature to 200°C (392°F) and cook for 5 minutes. Place a slice of Camembert on each mushroom. Top each with a tomato slice, then the remaining Camembert. Spoon the rocket paste on top and scatter with the remaining breadcrumbs.
Place on the lower rack of the halogen oven and cook for 5–10 minutes until the breadcrumbs are golden. Serve with grainy bread and a leafy salad or pak choi.