Preheat the oven to 180C.
Grease 3 x 7" cake tins and line the bottom with baking paper.
Mix together the pumpkin, sugars, oil, water, eggs and lemon zest. Beat until combined.
In another bowl sift together the flour, baking powder, salt and spices.
Add the dry ingredients to the wet ingredients and fold in until just combined.
Spoon equally between the 3 tins and smooth out the top.
Bake for 35 - 45 minutes or until a skewer comes out clean. Allow to cool and then carefully turn out from the tins.
Whilst they are baking or cooling, make the icing.
Mix the coffee with just enough boiling water to dissolve it. Allow to cool.
Beat the butter until light, fluffy and pale.
Add the icing sugar and beat until fluffy.
Add the cooled coffee and mix in well.
When the cakes are totally cold, trim down the tops so they are flat and even.
Sandwich together with the coffee frosting, so you have a stack of 3 cakes.
Coat the outside with the icing and smooth well, put the cake in the fridge.
Make the ganache by heating the cream until just bubbling. Remove from the heat and stir in the chocolate until fully melted and the ganache is thick.
Add food colour, a little at a time until the ganache is the colour you'd like. Allow to cool and thicken until it is spoonable consistency (you may need to put it in the fridge for this).
Remove the cake from the fridge and drizzle the ganache.
Add sprinkles and serve!