In a saucepan on medium heat add the light brown sugar, molasses, golden syrup, all of your spices (allspice, ginger, cinnamon and nutmeg) with the 2.5 tablespoons of water. Gently stir until well incorporated.
Now lower the heat a little and piece by piece add in the butter and stir until melted. Melting the butter down can take a little bit of patience at this stage.
Add in the teaspoon of bicarbonate of soda. Be aware that your mix may expand or froth a little bit at this point. It’s OK if it doesn’t though. Remove from the heat.
Now you can pour your syrup-like mixture into the bowl of a stand-up mixer once it has cooled down to around room temperature.
After pouring in your spice/syrup mix add in your plain flour and mix on a slow speed until a slightly sticky dough forms! Place in your fridge to chill for 2 hours at least.
Roll out your dough (around 5-6mm is a good thickness) onto a floured surface and cut out all your cookie shapes then place onto a lined cookie tray. Place back into the fridge for 30 minutes to chill and firm them up. This helps stop your cookies from spreading!