Here's a little info about what a Joconde imprime is:
A joconde imprime (French Baking term) is a decorative design baked into a light sponge cake providing an elegant finish to desserts/torts/entremets/ formed in ring molds. A joconde batter is used because it bakes into a moist, flexible cake. The cake batter may be tinted or marbleized for a further decorative effect.
The joconde imprime is then cut in to strips and shaped in a ring mold. It is filled with pastry cream or various other fillings, and served. Astheroshe says to imagine it as a trifle but in a mold made out of cake.
Overall it was really quite fun, and I hope to make it again. But next time with pastry cream!