what you'll need:
Make your favorite plain vanilla cake, then right before putting in cake tin, add as many blueberries as wanted. Cook as recipe directions say. While cooking, whip up a buttercream. My favorite is just plain butter (unsalted preferably) and icing sugar. You can mash up blueberries and add to icing if wanted. Garnish with fresh blueberries. Let cake cool for 10-15 minutes before icing.