I was given this recipe by a teacher friend, Dawn Wasden.
3/4 c. wine vinegar
1 1/2 c. oil (I didn't use this much)
3/4 c. sugar
1 t. dry mustard
1 T. poppy seeds
1/2 t. salt
1/2 pound sliced fresh mushrooms
1 red onion, sliced super thin
6 slices bacon, cooked crisply and broken
1/3 pound swiss cheese, grated
2 bunches spinach, chopped
Blend first six ingredients, then add mushrooms and sliced onions. Marinate in fridge overnight. Pour over bacon, cheese, spinach and lettuce. Toss well.