Remove the base of a springform cake pan, place the springform ring on its side, and balance the ring on top of a small casserole dish so that it doesn't roll away.
Slice the glazed donuts in half diagonally.
Run the packaged chocolate bar(s) under a stream of warm water until the chocolate inside has melted. Cut open a corner of the chocolate bar package, squeeze some chocolate around the top of a halved donut, and place another halved donut on top.
Place the donuts upright in the springform ring with the wider sides on the bottom.
Continue gluing the donuts together with melted chocolate and stacking them in the springform ring until you have an almost complete ring of donuts.
Once only a few donuts are left, puree the raspberries and powdered sugar with an immersion blender and pass the raspberry puree through a fine-mesh sieve to remove the seeds. Transfer the raspberry jelly to a piping bag and squeeze it into the collective donut hole in the springform ring.
Add the rest of the halved donuts to the springform ring to complete the donut cake. Let the chocolate set and then lay the jelly donut cake flat on a cake plate.
For the chocolate ganache frosting, combine the melted chocolate and heavy cream. Pour the chocolate ganache over the jelly donut cake and decorate with colorful sprinkles while the frosting is still warm.
