Preheat your oven to 180ºC/160ºC fan and grease and line a 9x13" traybake tin (or 9x12" if that's what you have!) with parchment paper.
In a pan, gently heat the unsalted butter, dark brown sugar and treacle together in a pan until smooth, allow to cool for 10 minutes!
In a large bowl, sift the self raising flour, ginger and cinnamon together and pour in the treacle mix – stir to combine.
Add in the eggs and stir to combine.
Finally, add in the milk and mix again.
Pour the mixture into the lined tin - it's quite a runny mixture so don't worry.
Bake in the oven for 35-40 minutes, or until baked through.
Once baked, leave to cool in the tin fully.
For the Decoration
Beat your unsalted butter on it's own for a few minutes to loosen it and make it lovely and soft!
Add in the icing sugar, and the spices, and beat again! Continue beating until the buttercream is lovely and fluffy and perfect!
If your buttercream is a little thick, add 1-2 tbsp of boiling water or whole milk and mix again to smooth.
Spread the buttercream onto the cake, and decorate with some gingerbread men, and gingerbread crumbs and some sprinkles. Enjoy!
Notes
This cake will keep in an airtight container for 3-4 days! The flavour keeps on getting better as the days go on.
You could add some stem ginger to the recipe if you like when you beat in the egg!
Instead of buttercream you can do a drizzle of icing hinted with ground ginger! Use 200g icing sugar, 2-3 tbsp of water (or as much as you need to get the consistency you want) and 1/2 tsp ground ginger.