1. Whisk flours, salt, and chopped pecans in a bowl.

2. In the bowl of an electric mixer fitted with the paddle attachment, beat butter and sugar on medium-high speed until smooth and light, about 1 minute. Add maple syrup, egg yolk, and vanilla; beat on medium until well combined. On low speed, gradually add flour mixture; beat until just combined. Dough should be smooth and pliable. Flatten into a square. Wrap in plastic; refrigerate until firm, 1 1/2 hours or overnight.

3. Preheat oven to 275 degrees. Line a baking sheet with parchment paper.

4. On a lightly floured work surface, roll out dough into a 1/2-inch-thick rectangle. Cut out squares using a 3-inch fluted square cutter; place 1 inch apart on prepared baking sheet.

5. Bake cookies, rotating sheet halfway through, until golden just around the edges, 1 hour to 1 hour and 15 minutes. Transfer to a wire rack to cool. Cookies can be stored in an airtight container at room temperature up to 4 days.