Cut the onion, carrot and celery stock.
Heat up the oil in a large pan, add the butter, then sautée the onion until golden.
Add the carrot and celery stalk and sautée for a further 3-4 minutes until they begin to soften.
Sprinkle the flour and add the stock, stir well and leave to cook until it thickens into a sauce.
Now the turkey and brussels sprouts can go in.
Give a good stir, season to taste with salt, pepper and add the chopped parsley.
Transfer to baking dishes, either a large one or 2 smaller ones.
Leave to cool for about 15-20 minutes, then sprinkle semolina over, that will prevent the puff pastry from becoming soggy.
Preheat the oven to 200 degrees C. (390 Fahrenheit)
Cut a lid from the puff pastry roll, and use your fingertips to seal the edges of the pie.
Use a sharp knife to make a few holes in the lid so that the steam can escape while in the oven.
Bake for 30-40 min until golden.