Instructions

1. Heat the butter in a nonstick deep ridge pan, add the onion and leeks and fry for 10 minutes until softened. Add mustard and flour and cook for 1 minutes, add the wine and stir with wooden spoon till smooth.
2. Slowly stir in the stock, cream and lemon juice, cook for 5 to 10 minutes until the sauce is thick enough to hold its shape. Taste and season with salt and pepper and additional lemon juice if needed.
3. Stir in the fish and shrimp and chopped dill, transfer to baking dish.
4. Wet with water the edge of the baking dish and fit the puff pastry on the baking dish. Add decorative puff pastry cut outs if you are feeling creative. Brush with mixture of beaten egg yolk with a splash of cream. Make a hole in the middle of the pastry and insert the piebird. Bake in pre-heated oven at 180 C for about 30 to 35 min. 

tip: if your oven is like mine, quite powerful; than you may wish to cover the puff pastry with a bit of foil for the last 15 minutes to avoid the pastry getting toooo dark.