Before starting this Blueberry Mousse Entremets recipe, make sure you have organised the necessary ingredients for the pistachio Dacquoise. For the pistachio Dacquoise: Pour the egg whites in the stand mixer recipient... ... the castor sugar... ... and the light brown sugar. Add both sugars before staring to whisk. Beat on medium speed for a few seconds... ... then increase to high speed until you obtain a stiff meringue. ...