Step 1

Heat oil in a large frying pan over medium heat. Add leek. Cook, stirring occasionally, for 5 minutes or until soft.

Step 2

Add flour. Cook, stirring, for 1 minute. Combine stock and cream in a jug. Gradually add stock mixture to pan. Bring to the boil. Reduce heat. Add mustard and 2 tablespoons dill. Simmer for 2 minutes. Reserve one-quarter of the sauce. Add fish and prawns to pan. Simmer for 5 minutes or until fish is just cooked through.

Step 3

Meanwhile, make Basic crepes: Sift flour into a bowl. Whisk milk and eggs together in a jug. Add milk mixture to flour. Whisk until well combined.

Step 4

Spray a medium, non-stick frying pan with oil. Heat over medium heat. Pour 2 1/2 tablespoons batter into pan. Swirl to cover base. Cook for 2 to 3 minutes or until light golden. Turn over and cook for 1 minute. Transfer to a plate. Cover to keep warm. Repeat with remaining batter.

Step 5

Preheat grill on medium-high. Spoon 1/2 cup seafood mixture over 1 crepe. Roll up to enclose filling. Place in a flameproof, ovenproof dish. Repeat with remaining crepes and filling. Spoon over reserved sauce. Top with breadcrumbs.

Step 6

Place dish under grill. Grill for 5 minutes or until lightly browned. Stand for 5 minutes. Top with remaining dill. Serve.