Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Cream softened unsalted butter and brown sugar together until light and fluffy, about 2-3 minutes.

Incorporate egg yolk and vanilla extract into the creamed mixture, mixing until smooth, about 1-2 minutes.

In a separate bowl, whisk together all-purpose flour and salt. Gradually add to the wet mixture, stirring gently until a soft dough forms.

Roll the dough into 1-tablespoon-sized balls and place on the prepared baking sheet, flattening each slightly and creating an indentation.

Combine chopped pecans, brown sugar, heavy cream, and vanilla extract to make the filling. Spoon into the well of each cookie.

Bake cookies for 12-15 minutes until edges are golden and filling bubbles slightly.

Cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.