Heat the oil in a large, heavy-based frying pan and cook the mushrooms over a moderate heat for 2–3 minutes, turning once, until they are softened. Place the mushrooms, stalk side up, on a foil-lined grill rack.
Add the tomatoes to the pan juices, and cook, stirring occasionally, for 4–5 minutes until the tomatoes are thick and pulpy. Add the tomato purée, beans and honey and continue to cook for a further 1 minute. Remove from the heat and stir in the parsley.
Divide the mixture between the mushrooms and arrange the slices of Gruyère or Edam over the top. Sprinkle the mushrooms with the Parmesan and place under a preheated hot grill for 2–3 minutes until golden and bubbling. Serve with slices of hot buttered wholemeal toast.