Salad for a crowd

1 head iceberg lettuce
1 bag spinach
1/2 red onion, sliced
1 1/2 c. sliced fresh mushrooms
3/4 c. grated Swiss cheese
1/2 lb. bacon, fried crisp and crumbled
2 c. croutons
1 c. sugar
1 tsp. salt
2 tsp. dry mustard
2/3 c. apple cider vinegar
2 c. vegetable oil
1 Tbsp. poppy seeds

Combine lettuce, spinach, onion, mushrooms, Swiss cheese, and
bacon in a large bowl. Toss to mix. For dressing mix all
remaining ingredients in a blender adding poppy seeds last.
Let dressing chill for at least an hour before serving.
Mix salad with dressing and garnish with croutons. (May
be made in smaller batches. Dressing will keep well in
refrigerator).