Finely chop pistachios and spread them in a single layer on a rimmed baking sheet. Set aside.

Using an electric mixer on medium speed, cream sugar and butter in a large bowl until mixture resembles texture of wet sand, about 3 minutes. Add egg, vanilla and lime zest and beat until just combined.

Whisk almond flour, potato starch, and salt in a medium bowl. Add to egg-sugar mixture and mix until just blended.

Divide dough into two balls. Roll each ball into a seven- inch-wide log, about one and a half inches in diameter. Roll logs in pistachios to coat; reserve remaining pistachios for decorating. Wrap logs tightly in plastic wrap or waxed paper and pop into the freezer for about one to two hours to firm up. 

Arrange racks in upper and lower thirds of oven; preheat to 350 degrees Fahrenheit. Line two rimmed baking sheets with Gefen Parchment. 

Bake cookies, rotating sheets halfway through, until undersides are golden, eight to 12 minutes. Transfer cookies to wire racks. Let one sheet cool completely before lining again with parchment and baking second batch, if you can’t bake them all in one batch.

Using a sharp knife, slice dough into 1/4- inch-thick rounds and arrange on baking sheets. Give the log a quarter turn after each slice so you don’t get a flat edge and log stays round. If your baking sheets are half sheet pan size (13 by 18 inches) you should be able to get 15 cookies per baking sheet. If they are smaller, just put 12 cookies per sheet. They spread a bit. 

While cookies are cooling, mix icing sugar and limejuice to make a glaze. Cover with plastic wrap so it does not dry out.

When cookies are cool, transfer to a wire rack. You can transfer glaze to a disposable piping bag or just drizzle it with a spoon or fork. Decorate cookies with lime glaze and while the glaze is still wet, sprinkle each cookie with a bit of zest and some of the leftover pistachios.