Rough chop cake donuts, being careful to keep the vanilla and chocolate donuts separate. Fold vanilla donut crumbs into white buttercreme and chocolate donut crumbs into chocolate buttercreme. Cover and chill until firm (about 4 hours). Roll into about 24 (1½ inch) truffles and place on a parchment lined sheet tray. Reserve in cooler. Line another sheet tray with parchment paper. Heat chocolate according to directions on packaging. Using a dipping fork, dip each truffle into melted white or dark chocolate. Shake off excess, and place on prepared sheet tray. IMMEDIATELY sprinkle on decorations or let chocolate set, then drizzle with remaining melted white or dark chocolate. Let truffles stand until chocolate is set.
This is a great use for day old donuts! If donuts are iced, simply place in the food processor whole, only adding additional icing if needed to bind the mixture.