Crab Soup

Bahan-bahan (4 porsi)

• 3 tablespoons unsalted butter
• 3 tablespoons all-purpose flour
• 4 cups half & half
• 1 teaspoon Dijon mustard
• 1 tablespoon Old Bay seasoning, (plus more for serving (see note))
• ¼ teaspoon salt
• ⅛ teaspoon freshly ground black pepper
• 2 tablespoons dry sherry
• ½ lb lump crabmeat, (picked over to remove any shells)
• Finely chopped chives, (for garnish)
• Lemon wedges, (for serving (optional; see note))