Beat 3 eggs on high speed about 5 minutes or until very thick and lemon colored. Gradually beat in 210g granulated sugar. Beat in 80g water and 1 tsp vanilla powder on low speed. Gradually add 100g flour, 1 tsp baking powder and 1 pinch of salt, beating just until batter is smooth. Pour into a pan of 38 x 25 cm. Spreading batter to corners. Bake 12 to 15 minutes at 190°C.
Loosen cake immediately from edges of pan; invert onto baking paper generously sprinkled with powdered sugar. Carefully remove foil. Trimm off stiff edges of cake if necessary. While hot, cover with the tin and let cool down completely.
In chilled medium bowl, beat 235g whipping cream, 2 tbsp granulated sugar and 1,5 tsp instant coffee on low speed until thouroughly mixed. Spread filling over cake. Put aside a bit for decorating a stump end. Roll up cake.
Beat 45g unsweetened baking cocoa and 75g softened butter on low speed until thouroughly mixed. Beat in 240g powdered sugar until mixed. Beat in 1,5 tsp vanilla extract and 1-2 tbsp of hot water until frosting is smooth and spreadable.
For tree stump, cut off a 5 cm diagonal slice from one end of cake. Attach stump to one long side using 1 tbsp frosting. Frost cake with remaining frosting. With tines of fork, make strokes in frosting to look like tree bark. Garnish with whatever you like.