Preheat the oven to 180 C/gas 4. If using frozen sausages, thaw them first, and if they are in casings, peel these off before using.
Heat the oil on a medium heat in a large frying pan, and once hot, cook the bacon pieces for 3-4minutes until crispy. Add the diced apple and cook for another 4-5 minutes until softened.
Crumble in the sausages and add the shredded vegan cheese and half of the vegan parmesan. Stir everything together until the cheese has melted, adding 1-2 tbsp plant milk if the mixture seems too thick. Set this aside and prepare the mushrooms.
Clean the mushrooms and remove the stems. Add a spoonful of the sausage mix (about 1 tbsp) to each mushroom and arrange them on a baking tray with the filling side facing up. Sprinkle the tops with the remaining vegan parmesan and bake for 30-45 minutes until the mushrooms are cooked through and piping hot. Serve immediately.
