2 cups uncooked small pasta shells
4 tablespoons butter
1 celery stalk, finely chopped
1 medium onion, chopped
3 tablespoons all-purpose flour
2 cups chicken broth (or vegetable broth)
2 cups milk (or half-and-half)
8 ounces Velveeta, cut into cubes
1 cup shredded cheddar (4 ounces)
1 teaspoon dry mustard
1 teaspoon Worcestershire sauce
½ teaspoon garlic salt
¼ teaspoon freshly ground black pepper
⅛ teaspoon (scant) cayenne pepper