Swiss Cheese Spinach Salad

My mom makes this salad a lot for Sunday Dinner. It' s delicious. We are not mushroom fans so we leave them out

1 (10 oz) bag spinach
1 large head iceberg lettuce
1/2 red onion, chopped
3/4 c. sliced fresh mushrooms
3/4 c. grated Swiss cheese
1/2 lb. bacon, cooked and crumbled
1 c. cottage cheese, drained
Mix together in large bowl.

Dressing:
1 c. sugar
2 tsp. dry mustard
1 tsp. salt
2/3 c. cider vinegar
2 c. vegetable oil
1 T. poppy seeds

Combine all dressing ingredients and mix well. Best after chilling overnight. Pour on salad just before serving and mix well.