3 tablespoons fresh breadcrumbs
2 tablespoons freshly grated Parmesan cheese
1 cup whole milk
2 bay leaves
3 tablespoons butter
1 tablespoon all-purpose flour
4 ounces grated sharp white cheddar cheese
Kosher salt and black pepper to taste
18 ounces fresh spinach (not baby), stems removed
4 scallions, trimmed, washed and finely chopped
1 pound backfin crabmeat, gently but carefully picked over for shell
Preheat oven to 375 degrees.
Combine the breadcrumbs and Parmesan cheese and reserve.
Put the milk and bay leaves in a small saucepan and bring just to a boil over medium heat. Remove from the heat, cover, and let steep for 5 minutes.
Meanwhile, heat the butter in a small saucepan over medium heat. Whisk in the flour and cook, whisking constantly, until golden, about 5 minutes. This makes a roux. Reduce the heat to medium-low. Remove the bay leaves from the milk and whisk the milk into the roux. Cook, whisking, until the mixture thickens. Stir in the cheddar and cook, stirring, until it melts into the sauce. Remove from the heat. Season with salt and pepper to taste.
Wash the spinach thoroughly. Place it in a large saucepan over medium-high heat and let it steam with the residual water just until it wilts. Drain. Squeeze dry with a clean kitchen towel. Chop. Season with salt and pepper to taste. Combine the scallions with the spinach.
Layer a pan as follows: Spinach, sauce, crab, spinach, sauce, breadcrumb/cheese mixture.
Bake for about 30 minutes until the sauce is bubbly and the gratin is hot through.