Deviled Crab with Sherry Sauce

Name: Deviled Crab with Sherry Sauce
Ingredients: 2 lb cooked king crab legs in shell, thawed if frozen and shells split lengthwise; 1/2 stick (1/4 cup) unsalted butter; 2 tablespoons all-purpose flour; whole milk; 1 large garlic clove, lightly crushed; 2 large egg yolks; 1/3 cup medium-dry Sherry; 1/2 teaspoon dry mustard; 1/8 teaspoon freshly grated nutmeg; 1/8 teaspoon cayenne; 1/2 teaspoon salt; 2 tablespoons finely chopped fresh flat-leaf parsley; 1/4 cup fine dry bread crumbs; 1/4 cup finely grated Parmigiano-Reggiano (1/2 oz)