In a large mixing bowl, combine the all-purpose flour, baking powder, and kosher salt. Whisk together until well blended. Set this dry mixture aside.
In another bowl, using an electric mixer, cream together the unsalted butter and granulated sugar until the mixture is light and fluffy, about 3-4 minutes.
Add the large egg, vanilla extract, and pistachio extract to the creamed butter and sugar. Mix well until fully incorporated.
Gradually add the dry flour mixture to the wet mixture, mixing on low speed until just combined. Be careful not to overmix.
Gently fold in the finely chopped pistachios. For more intense flavor, substitute some chopped nuts with pistachio flour.
Divide the dough into two equal portions, shape each into a disk, wrap in plastic wrap, and refrigerate for at least one hour to chill.
Preheat your oven to 350°F (175°C) and line your baking sheets with parchment paper.
On a floured surface, roll out one disk of chilled dough to about ¼ inch thick. Use cookie cutters to cut out shapes and place them on prepared baking sheets.
Bake the cookies for 8-10 minutes or until the edges are lightly golden. Watch carefully to avoid over-baking.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring to a cooling rack to cool completely.
In a microwave-safe bowl, combine green candy melts and vegetable shortening. Microwave in 30-second intervals, stirring until melted and smooth.
Dip cooled cookies into melted candy coating, letting excess drip off. Place back on cooling rack and sprinkle with colorful sprinkles while coating is wet.
Allow decorated cookies to set at room temperature until the coating hardens.