Chocolate-Pistachio Sablés- Gluten Free!

Serving Size  : 30   

1            cups  sweet rice flour
1/4        cup  tapioca flour
1 1/2    tablespoons  potato starch
1/4        cup  unsweetened cocoa powder
1/3       teaspoon  kosher salt
0.1       teaspoon  baking soda
1 1/4   sticks  unsalted butter — (2 1/2 sticks) room temperature
0.6       cup  light brown sugar — (lightly packed)
1/2      teaspoon  vanilla extract
2          large  egg white
2 1/2  ounces  bittersweet or semisweet chocolate — chopped
1/2     cup  unsalted — shelled raw pistachios, coarsely chopped
            Flaky sea salt (such as Maldon)

1)  Whisk flour, cocoa powder, kosher salt, and baking soda in a medium bowl. Using an electric mixer on high speed, beat butter, brown sugar, and vanilla until light and fluffy, about 4 minutes. Reduce speed to low and gradually add dry ingredients; mix just to combine, then mix in egg white. Fold in chocolate and pistachios.

2)  Divide dough into 4 pieces. Roll each piece into an 8″-long log about 1 1/2″ in diameter, pushing dough together if it feels crumbly. Wrap tightly in parchment paper and chill until firm, at least 4 hours. (The colder your dough, the easier it will be to slice.)

3)  Place racks in lower and upper thirds of oven; preheat to 350°. Working with 1 log of dough at a time and using a serrated knife, cut logs into 1/4″-thick rounds and transfer to 2 parchment-lined baking sheets, spacing 1/2″ apart.

4)  Sprinkle cookies with sea salt and bake, rotating baking sheets halfway through, until set around edges and centers look dry, 10-12 minutes. Transfer to wire racks and let cool.

DO AHEAD: Cookie dough can be made 1 month ahead; freeze instead of chilling. Slice frozen logs into rounds just before baking.