Preheat oven to 350° F. Line a cookie sheet with a Silpat or parchment paper.
Using the large holes of a box grater, grate the Almond Paste and the butter into a medium bowl. Add the flour, sugar, baking powder and salt, and mix together with fork or pastry blender until crumbly. Add almonds and chocolate chips, if desired.
In a separate bowl, whisk together egg whites and vanilla until frothy. Add to almond mixture. Mix until dough holds together. Turn out onto a lightly floured counter.
Roll dough into a 2-inch thick log. Cut in half and roll each piece 10 inches long. Transfer rolls to cookie sheet. Flatten to 3/4-inch thickness.
Bake 30-35 minutes or until golden. Cool cookie sheet on wire rack for 10 minutes.
Cut into 3/4" diagonal slices. Return to cookie sheet, cut side down. Bake 10-12 minutes or until golden. Flip and bake 10-12 minutes more. Cool on wire rack, and store in air-tight container for up to 3 weeks.