2) Transfer the sausage and onion to a frying pan, add the wine and cook until the wine is completely reduced. While the wine is reducing, break up the sausage into small pieces.
3) Add the spinach and water and season with salt and pepper. Cook until the spinach has wilted, about 2 minutes. Remove from the heat and stir in 2 tbsp of the basil, 2 tbsp of the parsley and the cheese. Allow to cool slightly.
4) Heat the griddle to high. Brush the mushroom caps on both sides with the remaining oil and season with salt and pepper. Place the mushrooms on the griddle, top side down, and cook until golden brown, about 4 minutes. Remove from the griddle and place on a flat surface, cap side down.
5) Fill the mushrooms with the sausage mixture and top each with a few slices of tomato. Season the tomatoes with salt and pepper and place on the griddle, cap side down. Close the cover and cook until the mushroom and filling have heated through, the cheese has melted and the tomatoes are soft, about 5 minutes.
6) Remove the mushrooms to a platter and sprinkle the tops with the remaining parsley and basil to serve.