Preheat the oven to 320°F (160°C) using the convection setting. Line a large baking sheet with parchment paper.
In the bowl of a stand mixer fitted with the whisk attachment, beat both sugars, the egg whites, and the whole egg until light and fluffy.
In a separate bowl, combine the all-purpose flour, flaxseed, baking soda, and salt. Add the vanilla extract to the egg mixture, then gradually incorporate the dry ingredients. Once combined, fold in the chocolate chips and almonds using a spatula.
Divide the dough into two equal portions and shape each into a log approximately 6 inches (15 cm) long. Place the logs on the prepared baking sheet, leaving enough space between them. Use two baking sheets if necessary.
Bake for approximately 30 minutes, or until firm. Transfer the logs to a wire rack and let cool for 10 minutes.
Using a serrated knife, cut each log diagonally into slices approximately ½ inch (1.5 cm) thick.
Reduce the oven temperature to 300°F (150°C), keeping the convection setting on. Return the biscotti to the baking sheet and bake for 7 minutes. Turn them over and bake for another 7 minutes.
Let the biscotti cool completely. Dip each one halfway into melted white chocolate, place on a parchment-lined baking sheet, and allow the chocolate to set. Use melted dark chocolate to draw the ghost's eyes, mouth and nose.