1/2 c. sour cream
1/4 tsp. salt
1/4 tsp. dry mustard
1 c. buttermilk
1 c. Hellmann's mayonnaise
3 tbsp. lemon juice
1/3 c. bleu cheese

Combine sour cream, salt, mustard, lemon juice, 1/2 cup buttermilk and mayonnaise; mix well. Add crumbled bleu cheese and remaining buttermilk. Let stand 24 hours before using.