Put the sugar, golden syrup and butter in a saucepan. Bring to a simmer, then bubble for 1-2 mins, stirring until well combined. Set aside to cool for 10 mins.
Tip the flour, bicarbonate of soda and spices into a large bowl. Add the warm syrup mixture and the egg, stir to bring everything together, then gently knead in the bowl until smooth and streak-free. The dough will feel a little soft now, but will firm up once cooled. Wrap the dough in cling film and chill for at least 30 mins.
Remove the dough from the fridge and and leave at room temperature until softened. Heat oven to 200C/180C fan/gas 6 and line two baking trays with baking parchment.
Working with half the dough at a time (keeping the remaining dough well wrapped), roll out to the thickness of a £1 coin, keeping the dough in a rough rectangle shape. Cut the dough into long strips, roughly 8cm wide, then cut each strip into ‘jumpers’ (see step-by-step). Cut out a V-neck for the collar and trim slim triangular pieces from either side to create sleeves (see step-by-step). Continue rolling and shaping the dough until you have about 20 jumper shapes. Arrange over the trays and bake for 8 mins until a few shades darker and puffed up a little. Cool on the trays for 5 mins, then transfer to a wire rack to cool completely. Un-iced, the biscuits will keep in a sealed container for up to 2 weeks.
For ‘flooded’ biscuits, mix 100g fondant icing sugar with enough water to make a thick but pipeable icing – it should hold its shape when piped. Transfer the icing to a piping bag fitted with a fine round nozzle and pipe a line around the edge of each biscuit. If you have any icing left, tip it back into a bowl and add the remaining icing sugar, then add enough water to make an icing a little looser than the first batch, but not too runny. Divide the icing between as many bowls as the number of colours you’d like to use, then add a tiny bit of colouring to each and mix well until you have a vivid colour.
If you have disposable piping bags, transfer the icings to different bags and secure the open ends (see tip).
To pipe your jumpers using the 'flooding' method, pipe the runnier icing onto the biscuit, then use a cocktail stick to encourage it to fill every corner up to the piped border. Once dry, you can add details like fluffy collars and cuffs or spots and stripes with the thicker icing.
To pipe your jumpers with a cable knit effect, pipe lines of coloured icing (we used white) vertically across the jumper. Use a toothpick to drag up and down through the icing to create
a wave effect.
Finish off with sugar sprinkles if desired - we used mini gingerbread men, snowflakes, white ‘mimosa’ balls and gold polka dot sprinkles (see tip).