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

Cream together the unsalted butter and light brown sugar until fluffy. Add the egg yolk and vanilla and mix until smooth. Gradually add flour and salt to form a soft cookie dough.

Scoop dough into balls and place on the baking sheet, pressing an indentation in each ball.

In a saucepan, combine chopped pecans, additional brown sugar, heavy cream, unsalted butter, vanilla extract, and a pinch of salt. Heat gently for 2-3 minutes until thickened.

Spoon the pecan filling into each cookie indentation without overfilling.

Bake in the oven for 10-12 minutes until edges are golden and centers pale. Allow to cool for 5 minutes on the sheet.

Transfer cookies to a wire rack to cool completely before serving.