Preheat the oven to 200°C/Fan 180°C/Gas 6.
Cut the baguette in half and with each half, make deep slits diagonally at 2cm intervals making sure not to cut all the way through. Place each on a large piece of foil.
Blend together the butter, garlic, parsley and walnuts, season and spread into the slits. Wrap loosely in foil and place both on a large baking tray.
Bake for 10 minutes, unwrap the foil to expose the top of the bread and cook for a further 10 minutes until golden and the butter has melted.