Coffee butter cream: Cut and work the butter to make it soft. Heat 7 cl of water with the sugar. Bring to a boil and continue cooking until 118 ° C. In the bowl of your mixer, whip the yolks and the eggs until frothy. When the syrup is at temperature, pour it little by little on the eggs. Keep beating to lower the temperature to 40 ° C. Then, gradually add the butter ointment. Beat vigorously to obtain an airy cream. Add the coffee aroma and beat again. Keep the cream at room temperature.
The sponge cake: Preheat the oven to 210 ° C (th.7). Beat the egg whites until stiff. Book them cool. Mix the yolks with the sugar with a mixer until the mixture whitens. Sift the flour and pour it on the mixture. Gently stir in the whites using a spatula, avoiding breaking the volume of the dough. Pour the dough on 2 plates lined with parchment paper. Bake for 10 minutes at 210 ° C. Carefully peel the sponge cake from the parchment paper. Then, soak them lightly with soaking syrup.
Cut out your strips of sponge cake before you start editing: you need 4 strips to line the sides of your mold and close it, and 4 other smaller strips to form the rectangle of sponge cake inside. Do not forget the 2 rectangles of sponge cake for the ends.
Line your mold with the large strips of sponge cake, and the 2 rectangles to make the ends. Garnish with buttercream 1 cm thick. Insert the 3 smaller strips, then garnish the cream center. Close with the 4th little strip of sponge cake, then finish with butter cream and finish with the 4th big band of sponge cake. Tamp well so that the log is rectangular. Place in the fridge for 1 hour 30 minutes.
Unmould your log at the coffee shop. Sprinkle with icing sugar and decorate sugar stars.