In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.

Beat in the egg yolk and almond extract until well combined.

In a separate bowl, whisk together the all-purpose flour, almond flour, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Divide the dough in half, flatten each half into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.

In a small bowl, combine the almond paste, softened butter, and almond extract. Mix until smooth.

Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.

On a lightly floured surface, roll out one disk of dough to about 1/8-inch thickness. Cut into 2-inch squares.

Place about 1 teaspoon of the almond filling in the center of each dough square. Fold the dough over the filling to create a small package, pressing the edges to seal.

Place cookies on the prepared baking sheets, about 1 inch apart.

Bake for 10-12 minutes, or until the edges are lightly golden brown.

Let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely.

In a small bowl, whisk together the powdered sugar and milk (or water) until you have a smooth glaze. Add more liquid if needed to reach desired consistency.

Drizzle the glaze over the cooled cookies. Immediately sprinkle with toasted sliced almonds.