Photographs: Martin Poole
Grease 2 baking sheets with butter. Put the flour, baking powder, ginger and butter in a food processor and whiz until it resembles breadcrumbs. Add the sugar and pulse to combine.
In a jug, beat together the golden syrup and egg, then add to the flour mixture. Pulse until it all starts to come together, then turn out and knead until you have a smooth dough. Wrap in clingfilm; chill for 30-45 minutes.
Preheat the oven to 200°C, fan 180°C, gas 6. Sprinkle a work surface with flour. Roll out the dough to 5mm thick, stamp out pumpkin and ghost shapes using cutters and place on the baking sheets. Reroll any trimmings and stamp out to make more biscuits – you should end up with about 20.
Bake for 12-15 minutes until lightly golden around the edges. Remove from the oven, leave for 5 minutes, then transfer to a wire rack to cool.
Put the royal icing sugar into a bowl and mix with 150ml cold water to form a thick icing. Divide the icing between two bowls. Colour one bowl of icing orange using the orange (or red and yellow) food colouring. Transfer 2 tablespoons of white icing from the other bowl into a small bowl and colour it black with food colouring. Cover with a damp cloth while you decorate the biscuits.
Get ahead: make a couple of days ahead; store in an airtight container. The uniced biscuits can also be frozen.
Kitchen secret: green fondant icing comes in a pack with three other colours, but you can also make it by kneading green food colouring into white fondant icing. Buy pumpkin and ghost cutters in store.