Bake the cake according to instructions and let cool. Crumble it up into bite-sized pieces for layering. Set aside.
In a chilled bowl, beat the whipping cream, powdered sugar and vanilla on high until gentle peaks start to form.
Before the whipped cream is completely done, add the vanilla pudding mix. This is going to stiffen it up pretty quickly, and will stabilize the cream so it stays that way.
Once cream has reached the desired consistency, layer it in a trifle bowl with the cake pieces, alternating layers until done. Finish with a layer of cream and top with fresh blueberries!
For best results, refrigerate at least 2 hours before serving. (But it can be served right away.)