Preheat the oven to 325 F. Line 2 cookie sheets with silicone or parchment paper. Set aside.

Place the flour, baking powder and salt into a food processor (16 cups sized bowl worked well for me, but it might have been ok in the 11 cup bowl--if you try leave a comment and let me know!). Pulse a few times to mix.

Add the pistachios and pulse a few times to begin to chop the nuts.

Add the well chilled butter. Pulse until it looks like bread crumbs.

Add the sugar and pulse to mix.

Whisk together the egg and orange blossom water in a small bowl.

With the processor running, add the beaten egg. Stop the processor as soon as it is evenly distributed. At this point, it will not come together as a dough, but instead will look like moist crumbs.

Clean and dry your counter. Lightly flour it. Dump the dough onto the counter, and, using your hands, gather it up and knead it a few times to form a cohesive dough (it will seem improbable but it will--and be certain not to overwork it--as soon as you have your cohesive dough, stop kneading).

Roll the dough out to 1/4-inch thickness on a lightly floured counter. Cut out the cookies using a cookie cutter or biscuit cutter, aiming for a 2 1/2-3 inch diameter.

Place the cookies onto the prepared cookie sheets, 1-2 inches apart (I got 12 to a sheet). Sprinkle with coarse sugar. Bake 2 sheets at a time--refrigerate the scraps until you can roll them out for a freed up cookie sheet. At the very end, after rolling out 36 cookies, I just patted out a large circle and baked it, because every time you roll out the dough the cookies will spread more.

Bake for 20-25 minutes, rotating the 2 cookie sheets top to bottom and front to back halfway through, until the cookies are browning at the edges and turning a light golden brown.