1cup unsalted butter at room temperature cut into 1 inch pieces
sanding sugar for sprinkling
Line several sheet pans with parchment paper.
In a small liquid measuring cup or bowl, use a fork to mix the eggs , triple sec, and vanilla together.
In the bowl of a food processor fitted with a blade, pulse the flour, granulated and confectioners sugars, orange zest, and salt together. Scatter the butter over the top of the flour mixture, and pulse until the mixture looks like wet sand, 8 to 10 one-second pulses. Pour the egg mixture over the top of the flour mixture, and pulse until the dough is smooth and starts to pull away from the sides of the processor, about 10 more one-second pulses.
Scrape the dough out of the processor and wrap it in plastic. Chill for 20 to 30 minutes in the refrigerator, just until it is cool to the touch, but not hard.
Flour a work surface, and roll the dough out somewhere between 1/8 inch and 1/2 thick (the thinner the dough, the crispier the shortbread, so this is a personal preference). Use a 1 1/2 inch biscuit cutter to cut out circles, then place cookies on the sheet pan, 12 to a pan. (If your shortbread circles stick to the counter at all, you can slide a spatula underneath to help move them to the baking pans). Extra dough can be rerolled to make more cookies.
Adjust an oven rack to the middle of the oven. Preheat the oven to 325 degrees.
Cover each cookie with the sliced almonds and gently press them into the dough. Generously sprinkle sanding sugar over the top, then chill each pan in the refrigerator for 15 minutes before placing in the oven.
Bake one pan at a time, rotating halfway through baking. Bake until edges are light golden brown, 13 to 14 minutes.
Leave cookies on the pans for 10 minutes, then transfer them to a wire rack to finish cooling and crisping up. Store cookies in an airtight container at room temperature for up to 4 days.