Preheat the oven to 200°C and line a baking sheet with baking paper.
Mix the walnuts, sugar, cinnamon and ginger in a bowl and set aside.
Dust the work surface with a little flour. Roll the puff pastry into a rectangle (3-4mm in thickness). Sprinkle three quarters of the walnut filling onto the pastry and spread evenly. Use a rolling pin to very gently press the filling into the puff pastry.
Fold the long sides of the rectangle in so that they meet in the middle. Sprinkle remaining filling over the pastry and use a rolling pin to gently press it into the pastry.
Fold the same sides over to meet in the middle again. Fold one half over the other and gently press together into a log.
Cut the pastry log into 1cm slices and arrange the slices on your baking tray. Bake for 25-30 minutes until the palmiers are puffed up and golden.