How to Make It
In a medium bowl, beat the butter with an electric mixer until pale and creamy, about 3 minutes. Gradually beat in the sugar until well blended.
In a small bowl, whisk the egg yolk with the maple syrup and vanilla. Drizzle the egg-yolk mixture into the butter, beating at low speed until incorporated.
Using a wooden spoon, stir in the flour and pecans. Divide the dough in half and shape into 2 disks. Wrap each disk in plastic and refrigerate until chilled, at least 2 hours or overnight. Let the dough stand at room temperature for 10 minutes before rolling it out.
Preheat the oven to 325°. Roll out each disk of dough 1/4 inch thick between 2 sheets of wax paper. Cut the dough into 2-inch rounds and transfer to baking sheets lined with parchment paper. Bake for 20 to 25 minutes, or until golden. Transfer the cookies to wire racks to cool.