Preheat the oven to 350 degrees F.
Line a large cookie sheet with parchment paper and set aside.
In a large bowl combine the all purpose flour, finely ground almonds, baking powder, salt, wild blueberries and chocolate chips.
Stir and set aside.
In a separate smaller bowl, whisk together the vanilla sugar, melted butter, eggs, lemon zest, vanilla extract and Limoncello liqueur.
Add the wet ingredients to the flour mixture and stir with a wooden spoon till thoroughly combined.
Transfer the biscotti dough to a lightly floured work surface and divide in two.
Dust hands with flour and roll 1 portion at a time into a 12 inch log.
Transfer logs to prepared cookie sheet.
Brush each log with the beaten egg white.
Bake in the preheated oven for 25 minutes.
Remove the cookie sheet from the oven and place the cookie sheet on a cooling rack and allow to cool for 10 minutes.
Transfer the logs one at a time to a cutting board and slice diagonally to about 3/4 inch pieces.
Place the sliced biscotti upright on the baking sheet and return to the oven to bake for an additional 15 minutes or till golden brown in color.
Transfer to a wire rack to cool.
Melt 1/2 cup of white chocolate in microwave safe bowl then thin it with a little bit of vegetable oil for easy drizzling.
Drizzle the biscotti with the melted white chocolate and allow the chocolate to set before serving.