Step 1 Preheat oven to 180°C. Melt spread in a large saucepan over medium heat. Cook fennel and leek, stirring, for 5–7 minutes or until softened. Add flour and stir to coat. Gradually add stock, stirring to combine. Add 1 cup milk. Reduce heat to low. Simmer for 10 minutes, or until fennel is tender and sauce thickens.
Step 2 Meanwhile, boil potatoes for 10–15 minutes, or until tender. Drain and return to pan. Add milk and mash until smooth.
Step 3 Add dill, fish, salmon, prawns and peas to fennel mixture. Cook for 5 minutes, until fish is just cooked through. Remove from heat.
Step 4 Spray 4 x 1 1/4 cup-capacity ramekins with oil. Spoon fish mixture into ramekins. Top with mash and spray with oil. Bake for 25 minutes, until lightly browned.