Melt the coconut oil and let it cool down. In the meantime, line a box mould (20 cm long) with baking or parchment paper. Cream eggs, icing sugar, salt and cocoa. Mix with the coconut oil.
Alternately fill in a layer of chocolate mixture and butter biscuits (put 40 g aside). Leave about 3 tablespoons of the mixture and cut the biscuits slightly if necessary. Finish with the layer of biscuits and chill the mould for 3-4 hours.
Turn the box mould over onto a board. Loosen the baking paper. Cut the chocolate biscuit cake straight all around. Put aside sections. Cut a door out of it. Pile the remaining pieces in the middle of the mould.
Support the rest of the butter biscuits in a roof shape. Brush them with the retained chocolate mixture. Attach the Mikado sticks to it. Support with empty biscuit boxes and let them cool down again.
Put the door against the cottage. Cut Japonais in half. Stick 2 halves to the house using the cream as a window. Fix the chimney as well. Dust everything with icing sugar.