Preheat the oven to 180C/350F/Gas 4.
Remove the stalks from the mushrooms and reserve them for the stuffing. Drizzle the mushrooms with two tablespoons of olive oil and season with salt and freshly ground black pepper.
Heat a griddle pan and fry the mushrooms, gill-side down, for a couple of minutes or until they are turning golden-brown.
Heat the remaining oil in a frying pan and gently fry the onion and garlic for about five minutes, or until softened.
Chop the mushroom stalks and add them to the pan along with the bacon. Fry for 4-5 minutes, or until slightly browned. Add the wine and simmer until slightly reduced. Stir in the cream and half of the cheese.
Turn the mushrooms over and pile in the filling. Top with the rest of the cheese and sprinkle with the chopped sage.
Place onto a baking sheet and transfer to the oven to bake for 6-8 minutes, or until the cheese has begun to brown. Serve warm.
