Preheat your oven to 200°C. Line a baking sheet with baking paper.
Combine the walnuts, sugar, cinnamon and ginger in a bowl. Set to one side.
Dust your 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. Spread the filling evenly over the pastry spreading it right to the edges. Use a rolling pin to very gently press the filling into the puff pastry. (This will help it to stick to the pastry.)
Fold the long sides of the rectangle in so that they meet in the middle. Sprinkle the remaining filling over the pastry and use a rolling pin again 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. Arrange the slices on your baking tray, allowing some space for spreading. (You can bake the palmiers in two batches if it’s easier!) Bake for 25-30 minutes until the palmiers are puffed up and golden.