In a mixing bowl, beat ½ cup of softened unsalted butter with 1 cup of powdered sugar using an electric mixer on medium speed for 2-3 minutes until light and fluffy.

Add ½ cup of pistachio paste, 1 large egg yolk, 1 teaspoon of vanilla extract, and ½ teaspoon of almond extract to the butter mixture. Mix for about 1 minute until fully combined.

In a separate bowl, whisk together 1¼ cups of all-purpose flour and ¼ teaspoon of salt. Gradually add this dry mixture to the wet ingredients and stir until just combined.

Scoop the dough into 1-inch balls and place them on a parchment-lined baking sheet, leaving space between each cookie.

Preheat your oven to 350°F (175°C) and bake the cookies for 10-12 minutes until the edges are golden. Cool on the tray for 5 minutes.

Mix another ½ cup of pistachio paste, ¼ cup of softened butter, and 1 cup of powdered sugar. Blend until smooth, adjusting with milk for consistency.

Spread the pistachio filling on the flat side of one cooled cookie and top with another cookie to create a sandwich. Optionally, dust with powdered sugar and sprinkle crushed pistachios.