Grease and line a deep loaf tin. I am using a bread tin.
In a small sauce pan heat the butter, milk, sugar, spices and treacle and candied ginger, until just melted.
Cool
Mix flour and bicarb, then stir into the mixture in the saucepan until no lumps remain.
Pour into the loaf tin and turn the oven down to 160 C / 320 F before placing it onto the middle rack and baking for 50 minutes.
A toothpick or knife should come out clean when inserted into the middle of the cake. Take ou and leave on a rack to cool. This cake will probably sink slightly when it cools
To make the Icing
Pour the icing sugar into the bowl of a food processor and whizz until there are no lumps.
Add the soft butter and vanilla and ginger powder. Process until combined and light.
Spread onto the cake and if you like, top with extra candied ginger
Notes
The icing can also be mixed by hand. You will need to sift the icing sugar first before making.