To make the filling, chop the mushrooms, garlic and green onions, and add them to a pan together with a bit of butter.
Leave to cook until the mushrooms are cooked and all the liquid is released.
Season with salt and pepper to taste, and add the chopped parsley, then leave to cool. Add the chopped walnuts, and stir to combine.
Pre-heat the oven to 200 degrees Celsius (390 degrees Fahrenheit).
Place the turkey breast onto a chopping board, and use a sharp knife to cut it horizontally, but not all the way through.
Open it up, then use a meat tenderizer to flatten it up to a cm (half an inch) thickness).
Spread the filling over the turkey breast, then roll it up, and use tooth picks to keep it together.
Place it in an oven-safe dish, then places a few butter cubes on top, sprinkle the paprika and garlic granules over, and add the bay leaves too.
Cover with a foil, then roast for 20 minutes, after that remove the foil, add a quarter of a cup of water, and cook for a further 50 minutes, basting occasionally.
Slice it up, and serve it either warm or cold.