Cream together the softened butter, brown sugar, and egg yolk in a mixing bowl until smooth and well combined.

Gradually incorporate the all-purpose flour into the wet ingredients, mixing until a dough forms.

Roll the dough into 1-inch balls.

In a separate small bowl, whisk the egg white until slightly frothy.

Dip each dough ball into the beaten egg white.

Roll the egg white-coated dough ball in finely chopped pecans, ensuring it's fully covered.

Place the pecan-coated dough balls 2 inches apart on ungreased baking sheets.

Slightly flatten each cookie before baking.

Bake in a preheated oven at 375°F (190°C) for 8-12 minutes, or until the edges are lightly browned.

Remove the baking sheets from the oven and transfer the cookies to wire racks to cool completely.