Step 1

In a medium bowl, blend flour and hollandaise sauce mix with 2 cups half-and-half.

Step 2

Melt butter in a medium, heavy saucepan over medium heat. Slowly add hollandaise mixture, stirring constantly until thickened. Add remaining half-and-half, Old Bay, dry mustard, celery seed, and whipping cream. Bring to a simmer and reduce heat to low. Add crabmeat and sherry, stirring gently until warmed through. Serve immediately.