Very gently un-roll the cooled cakes. Trim the very edges of each cake layer off (eat those scraps!). Re-roll each cake layer the same way but this time without the tea towel. Cut each log in half so you have four logs about 4 inches (10.5cm) long.
Unroll one of the logs very gently and spread 1/4 of the coffee cream over the surface of it. Re-roll the same way and stand the rolled log up like a tree trunk.
Unroll a second log of cake, spread on 1/4 of the whipped cream. Starting at the exposed edge of the 'tree trunk', wrap this second strip of cake around it.
Repeat with the next two cake logs so you end up with a very fat, short roll cake sat upright.
If your cakes crack/break in the process of doing this, don't worry about it. Just patch it back together with some cream and you really won't notice it!
Place onto a cake stand and frost the top with around 1/3 of the ganache - the ganache should have cooled to a spreadable consistency by this point. If it's too firm, place over a bain marie briefly to melt some of the ganache and then remove from the heat and beat together with a whisk. If it's too runny still, pop it into the fridge for a few minutes and check on it until you get the right consistency.
Use an offset spatula to smooth the ganache out to the edges. Then use the spatula to make a spiral pattern on the top of the cake (to look like tree rings). Next, frost the sides with the remaining ganache, smoothing out with an offset spatula before using the spatula to make upward strokes all around the sides to give it a 'bark' texture.
Chill until ready to serve.
(for decorations I've used plastic succulents on mine! I also like chopped hazelnuts, meringue 'mushrooms' or fondant 'mushrooms' or even some fresh fruit or edible flowers/greenery (like thyme or rosemary) to decorate).