Preheat oven to 325Fº and line a baking sheet with parchment paper.
Cream the shortening, granulated sugar, eggs, salt, almond extract, vanilla extract, and anise oil (or ground anise) together on medium-high speed until light in color and well combined, about 4-5 minutes.
Sift together flour and baking powder.
Slowly mix floured mixture into creamed mixture with slivered almonds until thoroughly blended.
Shape dough into long narrow loaves about 1 inch thick by 1 inch wide, and place them 3 inches apart on a greased baking sheet.
Bake at 325ºF for 25 to 30 minutes, then remove from oven and let cool for 20 minutes.
With a serrated knife, slice the loaves along the width to create your biscottis. Lie each biscotti back the baking sheet, leaving a little bit of room between each for even cooking.
Put your biscotti slices back in the oven for 20 minutes to brown and get crunchy.
Remove from oven and let cool on a rack for 10-15 minutes. Enjoy!