in a food processor, combine the butter and almond paste and pulse to combine.
Add the flour, sugar, baking powder and salt, and pulse until fully combined.
In the large bowl of your stand mixer with the whisk attachment, whisk eggs and vanilla until frothy. Add in the flour mixture from the food processor, and the slivered almonds and combine in the stand mix until a soft cookie dough forms.
On a lightly floured counter, divide the dough in half and roll each piece into long logs 10? long and ¾? thick. If the dough is too sticky, add in some more flour as needed.
Bake the two large pieces each on a cookie sheet lined with parchment paper at 350 degrees for 35 min. or until golden brown. Then allow the pan to cool for 5 min.
After cooling, cut into ¾? diagonal slices. Return to the cut pieces to the baking sheet, cut side down. Bake 12 min. Flip and bake 12 min. more until the biscotti are golden brown and dry. Cool on a wire rack.
Melt Belgium chocolate in a small bowl in the microwave at half power, and use an offset spatula to spread one side of the cookie, and allow to set at room temperature. Enjoy!