Pulse pistachios in a food processor until small crumbs form. See photo above for a visual. You need 3/4 cup of very finely chopped pistachios. Set aside.

Using a handheld or stand mixer fitted with a paddle attachment, beat the butter for 1 minute on medium speed until completely smooth and creamy. Add the confectioners’ sugar, vanilla extract, and almond extract, then beat on medium-high speed until combined. Add the flour, 3/4 cup pistachio crumbs, and food coloring (if using) and beat on medium-high speed until combined. The dough may not come together at first, but keep mixing. The cookie dough will be thick.

Cover the cookie dough tightly and chill in the refrigerator for 30 minutes and up to 3 days. (If chilling for 2+ hours, let the cookie dough sit at room temperature for at least 30 minutes before rolling into balls. The cookie dough will be very stiff after being in the refrigerator that long.)

prepare the brown butter icing (below) while cookie dough chills OR while cookies bake.

Preheat oven to 350°F (177°C). Line large baking sheets with parchment paper or silicone baking mats. Set aside.

Roll the cookie dough into balls, about 1 Tablespoon (20-22g) of dough each, and place dough balls 2 inches apart on the baking sheets. If the cookie dough is too crumbly, keep rolling and working it with your hands. The warmth of your hands will help bring it together.

Bake the cookies until lightly browned on the bottom edges and just barely browned on top, about 14-15 minutes.

Allow the cookies to cool for 5 minutes on the baking sheet, then transfer to a wire rack. Make sure cookies are cool to the touch before dipping in icing.

Slice the butter into pieces and place in a light-colored skillet. (Light colored helps you determine when the butter begins browning.) Melt the butter over medium heat, stirring occasionally. Once melted, the butter will begin to foam. Keep stirring occasionally. After 5-6 minutes, the butter will begin browning and you’ll notice lightly browned specks begin to form and a nutty aroma. Once browned, remove from heat immediately and allow to cool for 5 minutes. (The butter will eventually solidify, so don’t let it sit too long.) After 5 minutes, whisk in the rest of the icing ingredients until smooth. Taste. Add a pinch of salt, if desired. Add more confectioners’ sugar for a thicker texture, if desired. Likewise, add more milk to thin out if needed.

Dip cookies in icing or drizzle on top. If coated lightly, the icing will set after 1-2 hours. Cover leftover iced cookies tightly and store at room temperature for 1 day or in the refrigerator for up to 1 week. Cookies without icing can sit covered at room temperature for up to 1 week.