Blanch the mushrooms for 15-30 seconds, then leave to cool while you make the dressing. In a small bowl whisk together lemon juice and mustard. Season to taste. Add oil and whisk well.
In another bowl combine the spinach, mushrooms, bacon, onion and blue cheese. Drizzle with salad dressing before serving
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.