In a large bowl whisk together butter, sugar and Amaretto until fully combined and creamy. In a separate bowl whisk together the dry ingredients: flour, baking powder, ground almonds and salt.
Add the flour mixture, 1 cup at a time to the butter mixture, and whisk until fully combined after each addition.
Using your hands, roll the dough into small balls and flatten slightly.
Place on a parchment lined cookie sheet.
Bake for 7 to 12 minutes. It all depends how thick your cookies are. Start checking at the 7 minute mark, and if the sides and bottom of the cookies are slightly golden they are ready. Keep in mind that the top/center of the cookie will be soft, it will harden once the cookies cool down.
Remove cookies from oven and let them cool on the cookie sheet. Once cool you can move them to a cooling rack, being gentle not to crush them.
Wait for the cookies to be completely cooled before adding the glaze.
Combine all the ingredients into a medium bowl until the mixture has no lumps. If the mixture is too thin, add more sugar, 1 tablespoon at a time. If the mixture is too thick, add more liquid, 1 tablespoon at a time.
Drizzle a spoonful of glaze on top of the cookies and immediately sprinkle slivered almonds on top.
Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.