Mix your icing sugar into your water. Mix on a slow speed for 5 minutes, then a high speed for about 8 minutes. I do this in my stand mixer but you could do it with an electric hand mixer or by hand... it would just take longer.
Divide the icing up equally into smaller bowls - one bowl for each colour you'll need. I just had two bowls, one for my white icing and one for my red. Mix the red colouring gel into the bowl reserved for your red icing. Make sure you mix your colour in thoroughly so it's evenly throughout the batch.
Grab one more bowl and split the red icing again so you now have two bowls of red icing. To one bowl, add around 2 tsp of cold water and mix thoroughly until you have a slightly runnier mixture. We'll call that bowl your 'flood icing'. Put to one side for a minute.
Spoon your white icing into a piping bag, and tie up the top so it doesn't dry out - we won't need it for a while. Then, spoon your red icing into a piping bag (NOT your flood icing bowl) and snip off a very small hole to pipe from.
Simply pipe the outline of your Christmas jumpers onto your gingerbread men. Allow this to set for 5 minutes.
Then, grab another piping bag and fill it with your red flood icing. Pipe a nice dollop into the middle of the gingerbread man's jumper, leaving a half cm gap away from all edges of the outline you piped earlier. Don't use too much icing or it'll defo overflow!
Using a cocktail stick, now swirl the icing so that it meets the line, but be careful not to go over it.
Once you've repeated icing steps 5-7 on all of your gingerbread men, place them onto a baking tray and pop them back in the oven at 55C for 40 minutes.
Once the icing is really nice and set, grab your white icing piping bag and snip off a small hole to pipe from. Use this to pipe detail onto the gingerbread man's jumper. I usually did an outline of the jumper, followed by a few dots which hopefully looked like snow!
Allow this to set for 10 minutes and enjoy!