Heat the oven to 350°F/180°C. Spread the pecans on a baking sheet and toast until lightly browned and fragrant, about 12 minutes. Let cool completely.
In a stand mixer bowl fitted with the paddle attachment, or in a food processor, combine the butter, flour, powdered sugar, and salt. Mix until the mixture resembles coarse crumbs with no large pieces of butter remaining.
Add the egg yolks and mix just until the dough comes together. Wrap and refrigerate while you prepare the filling.
Place the blonde chocolate in a microwave-safe bowl and melt in 20-second intervals, stirring until smooth. Transfer the toasted pecans, melted chocolate, and salt to a food processor and process until smooth and spreadable.
Divide the dough in half. Working with one piece at a time, roll the dough between two sheets of parchment paper into a rectangle about ⅛ inch/2.5 millimeters thick.
Spread half of the filling evenly over the dough, leaving a small border around the edges. Starting from a long side, roll the dough into a tight log. Repeat with the remaining dough and filling.
Freeze the logs until firm, about 45 minutes.
Heat the oven to 340°F/170°C.
Transfer the logs to a parchment-lined baking sheet and bake until the cookies are set and lightly golden, about 20 minutes. Do not overbake.
Let the logs cool completely on the baking sheet. Dust generously with powdered sugar, then slice into ½-inch/1.25-centimeter-thick cookies and serve.