Preheat your oven to 350 degrees and line a baking sheet (or two) with parchment paper. Then, in a mixing bowl, combine the almond paste and butter. Add the flour, sugar, baking powder, and salt to the butter mixture and use a fork to combine until crumbly. Stir in the almonds and set aside.
Next, in another mixing bowl, whisk together the egg whites and vanilla. Add to the flour mixture and mix until the dough holds together. Then, on a lightly floured counter, roll the dough into a 2 inch thick log. Cut into two pieces; roll each 10 inches long and flatten to ¾ inches. Then, transfer to parchment lined baking sheets.
Bake for 35 minutes or so, or until golden. Then, cool the sheets on a baking rack for about 10 minutes. Slice into ¾ inch diagonal slices using a serrated knife. Then, return the slices to the cookie sheet, cut side down, and bake 10 minutes. Flip and bake 8-10 minutes. Remove from oven and let cool completely before serving.
Want to make this almond delight even better? Try drizzling it with or dipping it in melted chocolate for an extra special treat. So delicious!