Lightly oil the semisphere cavities with vegetable oil spray.
Cut out circles in your cake sheet (about 1.5 cm thickness) to desired diameter size to fit the semisphere using a circle cutter.
Brush the top with fruit preserves, jam or sugar syrup to help the cake adhere to the mousse.
Pipe in chilled chocolate mousse into cavities and let it set in the freezer for a few minutes.
With a heated spatula (heated under hot water and wiped) level all the spheres.
With a small spoon, create a cavity in the middle of the chocolate mousse.
Spoon in pannacotta mixture (before it sets) into the middle and transfer back to the freezer for a few minutes until panacotta sets.
Level the spheres with a heated spatula.
Transfer the cake circles (with the sticky side down) and press down gently to make sure cake is sticking to the chocolate mousse. Chill this for a few minutes until mousse is set perfectly and cake is adhered.
Unmould the chocolate mousse (this is easier to do, the more the chocolate mousse is set - if it is soft, it will be harder to take out).
Smooth the sides and transfer to a wire rack. placed over a CLEAN, DRY, CAKE SHEET, so you can collect the excess glaze.
When the glaze is cooled pour over the semisphere.
Chill the coated cakes.
Repeat this process at least three times, until a glossy smooth coating is achieved.