Step 1

Preheat oven to 375°F. Thinly slice scallions, separating dark green parts from white and light green parts; set aside.

Step 2

Beat cream cheese, mayonnaise, sour cream, salt, Worcestershire sauce, hot sauce, vinegar, and celery salt in the bowl of a stand mixer fitted with a paddle attachment on medium speed until creamy and smooth, 30 seconds to 1 minute, stopping to scrape down sides of bowl as needed. Add 1 cup each of the Cheddar and Havarti, and beat on medium-low speed until incorporated, about 10 seconds. Remove bowl from stand mixer, and fold in crabmeat and white and light green parts of scallions.

Step 3

Transfer crab mixture to a 2-quart baking dish, and top with remaining ¼ cup each Cheddar and Havarti. Bake in preheated oven until edges are bubbly and cheese is melted, about 20 minutes. Turn oven to broil, and continue baking until cheese is browned, 3 to 5 minutes. Remove from oven, and set aside to cool slightly, about 10 minutes. Top with reserved dark green parts of scallions, and serve with endive leaves.