6ozpecans, divided (either halves or shelled pecans will work)
1 3/4call-purpose flour
1/2tsp.fine sea salt
3/4cpacked light brown sugar
1tsp.vanilla bean paste or pure vanilla extract
Turbinado or maple sugar, for dusting (optional)
Add half the butter (4 ounces) to a medium skillet and melt over medium heat. Swirling the butter occasionally, continue cooking until it starts to bubble and foam and golden bits begin to appear; as the butter starts to brown it will produce a rich, nutty aroma. Watch closely now — it can burn quickly! — and remove the pan from the heat as soon as the butter reaches a medium caramel shade. Transfer the butter to a heat-proof bowl and set aside to cool for at least 20 minutes.
Place 1/2 cup (2 ounces) pecan halves (or shelled pecans) and granulated sugar in the bowl of a food processor and pulse until it becomes a medium-coarse, powdery meal. Measure 1/2 cup of the pecan meal into a medium mixing bowl, discarding any excess. Add the flour, cornstarch, salt, and baking powder to the bowl and whisk to combine.
Place the remaining half of the butter (4 ounces) butter in the bowl of a stand mixer fitted with the beater blade. Cream the butter on medium speed for 2 minutes, until creamy and pale. Add the the brown sugar and continue beating on medium speed for 4 minutes, until fluffy and light. Add the cooled brown butter and beat for another 1 to 2 minutes, until smooth.
Reduce the mixer speed to low and stir in the egg yolk and vanilla bean paste. Turn off the mixer and add the flour mixture. Return to low speed and mix until ingredients are just combined. Scrape the dough down the sides of the bowl and refrigerate for 20 minutes.
Turn the dough out on a clean work surface and divide in half. Place one portion onto a sheet of parchment paper and begin rolling into a log, using the paper, not your hands, as a guide. (Think rolling sushi!) Continue rolling and smoothing until you’ve got a log about 10-inches in length and 1-1/2 inches in diameter — it should resemble a paper towel tube. Repeat with the remaining dough.
Refrigerate for 3 hours or overnight, until firm; alternately, you can freeze the dough for about an hour. (Dough can be frozen at this point for up to three months. Thaw before proceeding.)
Before baking, preheat oven to 325°F. Remove the dough from the refrigerator and roll (like a Play-Doh log) on the counter to smooth and round out, if necessary. Slice the logs into 1/4-inch thick coins and transfer to a Silpat or parchment-lined baking sheet, leaving about an inch between each round. (Feel free to smooth the rounds with your fingertips, if needed.) Gently press a single pecan half into each cookie and sprinkle the tops with turbinado or maple sugar, if desired.
Bake the cookies, turning the pan 180 degrees halfway through cooking, until lightly golden and slightly puffed, about 13 to 15 minutes. Allow to cool on pan for 15 minutes, then transfer to a wire rack and cool completely. Cookies will keep, sealed in an airtight container, for up to one week.