Rose Pistachio Shortbread Cookies take the best ever shortbread cookie recipe and add a fresh twist with crushed pistachio nuts and a pink rose petal icing.
In the bowl of a stand mixer or in a large bowl with a hand mixer, beat butter, granulated sugar, brown sugar, and vanilla on medium-high speed until light and fluffy, 3-5 minutes.
Scrape sides of bowl with a spatula and while mixer is running on low speed, slowly add flour and 1/2 cup crushed pistachios and beat to just blend, taking care not to over-mix.
Divide dough in half and place each half on a large piece of plastic wrap. Fold plastic wrap over dough to completely cover and use your hands to roll the dough into a smooth log, about 2" or 2 1/4" in diameter. Repeat with second half of dough and then place in fridge to chill until firm, about 2 hours.
Pre-heat oven to 350 degrees and line a rimmed baking sheet with parchment paper. In a small bowl, mix together decorative sugar and remaining 1/3 cup crushed pistachios. Taking one dough log out of the fridge at a time, brush the outside of each log with egg wash and roll in decorative sugar and crushed pistachios.
Slice each log into ½"-thick rounds and arrange on prepared baking sheet about 1" apart. Bake for 12-15 minutes, until edges are just beginning to turn golden. Let cool slightly on pan before moving to wire racks to cool completely before icing.
Dip cooled cookies in rose icing and sprinkle on additional crumbled pistachios and crushed rose petals. Let icing harden before serving.
In a small saucepan over medium heat, bring milk and rose petals to just a boil.
Remove saucepan from heat and let roses steep in milk for about 10 minutes.
Strain and discard roses. Let mixture cool to room temperature.
Place 6 Tbsp of the rose milk mixture into a medium bowl and whisk in confectioners' sugar until smooth. For a thinner icing, add more rose milk, 1 tsp at a time.
Add pink food coloring until you reach desired shade.