Elegant hot crab dip

Ingredients

• 1-1/2 cups French white bread, crusts removed and cubed
• 1 cup whole milk
• 2 teaspoons butter
• 1-1/2 teaspoons fresh tarragon, minced
• 1/2 cup white onion, grated
• 16 ounces whole lump crab meat
• 1/4 cup heavy cream
• 1/4 teaspoon Cayenne pepper
• Kosher salt and freshly ground black pepper
• 2/3 cup Parmesan cheese, freshly grated
• 1 baguette, cut into 1/4-inch slices and toasted