How to Make It
Soak pecan or cherry wood chips in water for 20 minutes; drain. Light charcoal chimney starter filled halfway with briquettes. When briquettes are covered with gray ash, pour them onto the bottom grate of the grill, and push to one side of the grill. Scatter soaked wood chips over the hot coals. Adjust vents as needed to maintain an internal temperature of 200°F to 250°F. (If using a gas grill, place soaked wood chips in an aluminum foil packet; poke several holes in packet. Place packet directly on burner on one side of grill. Turn on the gas on that side to medium-high heat [350°F to 400°F], keeping the other side unlit.) Place the pistachios in a disposable aluminum pan or atop two sheets of heavy-duty aluminum foil (crimp the edges of the foil upward to create a rim and prevent the nuts or sees from sliding off) on unoiled grates over the side without the coals (or unlit side of gas grill). Grill, covered, until pistachios are slightly darkened and fragrant, about 30 minutes. Let cool completely, about 15 minutes.
Combine the flour, powdered sugar, lemon zest, and salt in bowl of a food processor, and pulse a few times to combine. Add the butter, smoked pistachios, and egg yolk, and pulse until the mixture forms a moist, sticky ball, 1 to 2 minutes. Transfer the dough to a work surface, and use a bench cutter to divide the dough in half. Form each half into an 8- x 1 1/2-inch log, then wrap the logs in plastic wrap and refrigerate until very firm, at least 4 hours or up to 5 days.
In a small bowl, whisk together honey, thyme, and lemon juice; set aside.
Preheat oven to 325°F. Line two rimmed baking sheets with parchment paper. Slice the logs into 1/2-inch rounds, rolling the log as needed to retain its round shape. Place the rounds on the prepared baking sheet, spacing them 1 inch apart. Sprinkle lightly with flaky salt, if using, and bake the cookies in preheated oven until lightly golden, 16 to 18 minutes. Let cookies cool on pan for 5 minutes; drizzle with honey mixture. Transfer to a wire rack to cool completely, about 10 minutes. Repeat with remaining dough and honey mixture.