Fry bacon until crisp, reserving fat. Crumble and set aside. Boil eggs until hard. Separate the yolks from the white. Chop each separately.
Combine all the dressing ingredients in blender. Blend until smooth.
To serve, toss spinach with dressing to coat lightly. Arrange leaves on salad plate. Garnish with egg, bacon, onion, mushrooms, and blue cheese, if desired.