Fishy dishy

250g fish pie mix (available in the supermarket haddock, cod, salmon)
150g king prawns defrosted
3 tbsp olive oil
50g salted butter 
2 leeks sliced
100g butternut squash cubed
1 tbsp dried thyme 
100ml white wine
3 tbsp plain flour
250ml hot fish stock (or chicken or vegetable)
200ml milk
2 tbsp sour cream 
1 sheet ready rolled puff pastry

1) Melt the butter in a large pan with the oil. Add the leeks, thyme  and butternut squash and cook for 5 - 10 mins.  Pour in the wine and let it bubble for 3 mins then add the flour and cook for 1-2 mins. 

2) Slowly add the stock, stirring until smooth and simmer and reduce for 5 mins. Stir in the milk, reduce the heat and simmer for 3 mins or until the sauce thickens. Stir in the sour cream and season with salt and pepper. 

4) place the fish and prawns in an ovenproof dish and cover with the sauce. Cover with the pastry, brush with milk and cook in an oven at 180 degrees for 30 mins until golden and bubbling.