Arrange spinach leaves on plates or a serving platter.
Cook bacon until crispy in a large sauté pan. Remove bacon, drain excess fat and return pan to medium heat. Add 2 tbsp (25 mL) of oil and mushrooms and sauté for 2 to 3 minutes, until soft but not fully cooked. Stir in garlic dry mustard powder. Add vinegar, season lightly and stir for one minute. Stir in remaining olive oil, remove from heat and adjust seasoning. Spoon dressing over spinach leaves and top with reserved bacon, chopped egg and red onion.
Taken from Anna and Michael Olson Cook at Home - Whitecap Books 2005.