- For filling:
- 1 medium leek (white and pale green parts only), cut into 1/2-inch pieces
- 1/2 cup finely diced carrot
- 1/4 cup finely diced celery
- 3 tablespoons unsalted butter
- 2 tablespoons all-purpose flour
- 1 1/2 cups whole milk
- 3/4 teaspoon salt, divided
- 1/4 teaspoon black pepper, divided
- 1 1/4 pounds skinless cod or scrod fillet, cut into 3/4-inch chunks
- For biscuit crust:
- 1 1/2 cups all-purpose flour
- 1 tablespoon baking powder
- 3/4 teaspoon salt
- 7 1/2 tablespoons cold unsalted butter, cut into 1/2-inch cubes
- 9 tablespoons whole milk
- 2 1/2 tablespoons chopped fresh dill
- 1 tablespoon unsalted butter, melted
- Put oven rack in middle position and preheat oven to 450 degrees F.
- Make sauce for filling: Wash leek in a bowl of water, then lift out and drain well. Cook leek, carrot, and celery in butter in a 2- to 3-quart heavy saucepan over moderate heat, stirring frequently, until tender, about 7 minutes. Add flour and cook, stirring, 1 minute. Stir in the 1 1/2 cups whole milk, 1/4 teaspoon salt, and 1/8 teaspoon pepper. Bring sauce to a boil, stirring, then reduce heat and simmer, stirring occasionally, 4 minutes. (Sauce will be thick.) Remove pan from heat.
- Make crust: Whisk together flour, baking powder, and salt in a bowl. Blend in butter cubes with your fingertips or a pastry blender until mixture resembles coarse meal. Stir in the 9 tablespoons whole milk and dill with a fork until mixture just comes together.
- Gather dough into a ball, then turn out onto a lightly floured surface and knead 2 or 3 times. Roll out with a floured rolling pin into an 8-inch square (1/2 inch thick), then cut out 4 biscuits using cutter.
- Make filling and bake pies: Sprinkle cod with remaining 1/2 teaspoon salt and 1/8 teaspoon pepper. Bring sauce to a simmer and stir in fish, then divide among ramekins. Top each ramekin with a biscuit, then brush biscuits with melted butter. Arrange ramekins in a shallow baking pan and bake until sauce is bubbling and biscuits are golden, 12 to 15 minutes.