happy_stomach and I were just discussing your cake over lunch! I'm no expert, but I ruin cakes all the time and therefore have a couple ideas (though trifle sounds good to me - you've basically got a trifle now, all you have to do is cut it into cubes and add some whipped cream)
First of all, where is the break? Is it only one layer, is it across the top, did it break in half completely? If it's just across the top, looks like you could hide it with the chocolate curls and the topping. If it's the sides, I agree that frosting the sides would be the way to go; you could then coat in crushed pistachios.
Do you have room in your freezer for the entire thing? See if you can tease a springform ring around it to hold it back together and freeze until it's solid. Regardless of where the break is, this will probably help whatever fix you come up with. I would then make a ganache with the white chocolate (sometimes this can be tricky, find and follow a recipe) but do it thicker than you would for a frosting - that is, use the proportions for a chocolate truffle. Warm it enough to be spreadable, and spackle your frozen cake back together. Then artfully using chocolate curls, pistachios, and crystallized ginger, cover up your mistakes.
You could also cover with stabilized whipped cream at the last minute, piped out of a piping bag with a star tip (
my personal favorite way to cover mistakes) Again, having the cake VERY VERY cold will help a lot.