Mix the following ingredients in a blender, or with an electric mixer. Prepare a day ahead.

1/3 c. finely chopped onion
2 c. real mayonnaise (not Miracle Whip)
1/2 c. chopped fresh parsley
2 cloves garlic, crushed
2 tbsp. anchovy paste
1 c. sour cream
1/2 c. wine vinegar
2 tbsp. fresh lemon juice
1/2 lb. bleu cheese, crumbled