Maryland Crab Bisque

2 tablespoons butter
1 cup minced celery
2 (10 ounce) packages white sauce mix
2 cups half-and-half
1/3 cup dry sherry
12 ounces crab meat (fresh, frozen or canned)
Salt and pepper, to taste
1 (13 3/4 ounce) can chicken broth

In a 3-quart saucepan melt butter and saut