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

In a mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until fluffy.

Beat in the egg and vanilla extract until well combined.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add this mixture to the wet ingredients, mixing until just combined.

Roll the dough into 1.5-inch balls and place them on the prepared baking sheet. Use your thumb or a spoon to create an indentation in the center of each ball.

Chill the cookie dough balls in the fridge for 15 minutes.

In a small bowl, combine the chopped toasted pecans, brown sugar, corn syrup, melted butter, vanilla extract, and a pinch of salt for the filling.

Remove the cookies from the fridge and fill each indentation with about 1 teaspoon of the pecan filling.

Bake in the preheated oven for 10–12 minutes or until the edges are golden and the filling is bubbling.

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