• Preheat the oven to 180oC/160oC fan/350oF. 
• Grease and line a 23 x 33 cm (9 x 13-inch) rimmed baking tray with baking paper. 
• In a large bowl, mix the flour, cocoa powder, sugar, baking powder and bicarbonate of soda. Add the water, pumpkin puree and oil. Stir until smooth. Pour into the prepared baking tray and spread out in an even layer. 
• Bake for 20-25 minutes until a skewer inserted into the centre of the cake comes out clean.
• Take a clean tea towel and dust with a generous layer of icing sugar. Tip the hot cake out onto it. Trim the chewy edges of the cake off to make rolling easier. Starting at the short side, roll the cake up (keeping the baking paper on it to stop it sticking to the towel) along with the towel, as though the towel is the 'filling' of the cake. Set in the fridge for at least 6 hours to cool completely. 

Make the filling:

• Cream the butter and cream cheese until smooth. Mix in the icing sugar and cocoa powder. Mix in the coffee, starting with 1 tbsp and adding more if needed to make it spreadable. Chill until needed.

Make the coating:

• Mix the melted chocolate with the butter in a bowl until smooth. Stir in the icing sugar then mix in the coffee. Take 3 tbsp of the filling you made earlier and mix it into the melted chocolate mixture. Set aside until later. 

Assemble:

• Gently unroll the cooled cake. Spread the filling over the cake in an even layer. Gently roll up. Cut 1/4 of the cake off at an angle then stick to the main roll of cake so it looks like a branch. Cover with the coating (you may need to re-warm it if it's too solid) and use a fork to make 'bark' texture in the coating. 
• It's best if you chill the cake for a couple of hours before serving so it has time to firm up before you cut it. Dust with icing sugar just before cutting to make it look snowy!