Whisk mayonnaise and sour cream in a mixing bowl until smooth with no lumps for even flavor distribution.
0.5 cup mayonnaise, 0.5 cup sour cream
Add minced garlic, lemon juice or vinegar, Worcestershire sauce, salt, and black pepper; whisk until fully combined and creamy.
2 cloves garlic, 1 tbsp lemon juice, 1 tsp Worcestershire sauce, 0.5 tsp salt, 0.25 tsp black pepper
Gradually add buttermilk 2 tablespoons at a time, whisking well after each addition until the dressing reaches a pourable consistency but still clings to a spoon.
0.33 cup buttermilk
Crumble blue cheese into pea-sized chunks and fold gently into the dressing to maintain texture contrast.
4 oz blue cheese
Transfer the dressing to an airtight container and refrigerate for at least 1 hour to allow flavors to meld and the texture to firm.