Place a sheet of baking paper on an oven tray. Grate the Parmesan and place them in small piles on the baking paper.
Sprinkle the pistachios over the parmesan piles. Chop the walnuts and spread them over the parmesan.
Place the tray in the middle of the oven at 200 degrees and bake for about 5-10 minutes or until the cheese is a nice golden brown color. Then remove the tray and leave to cool.
Cold mulled wine
Pour into glasses and serve well chilled, possibly with a few ice cubes depending on which glass you use. Decorate with blueberries, cranberries, a cinnamon stick, a sprig of rosemary, or anything else for a Christmassy touch.