Preheat the grill to medium.
For the salad, place the spinach into a large bowl, drizzle over the balsamic vinegar and olive oil and stir to coat the leaves.
Heat a frying pan and fry the bacon for 3-4 minutes, until crisp. Add the mushrooms and fry for 3-4 minutes. Add the bacon and mushrooms to the bowl with the spinach and stir well.
For the cheese toast, place the toasted ciabatta slices onto a baking sheet, top with the cheese and grill until the cheese is bubbling and melted.
To serve, place the salad into a serving dish and top with the cheese toast.