Grind roasted pistachios in a food processor until the texture of coarse cornmeal. Using a hand mixer, or by hand, cream together the butter, sugar, and kosher salt until light and fluffy, about 2 to 3 minutes.
In a small pan on the stovetop, melt your unsalted butter. Remove from heat. To the butter, add whole milk and then your egg. Whisk to combine.
In the bowl of your stand mixer, place all-purpose flour, kosher salt, instant yeast, and granulated sugar. Use paddle attachment to combine them.
Switch to dough attachment, increase to medium speed, and knead dough for 3 minutes. Turn off mixer to check consistency.