Beat the softened butter, brown sugar, and granulated sugar together until light and creamy.
Add the eggs and vanilla extract and mix until combined.
Add the flour, baking soda, salt, and cornstarch. Mix just until a cookie dough forms.
Fold in the chocolate chips and finely chopped pecans.
Cover the bowl with plastic wrap and refrigerate the dough for at least 1 hour or up to 24 hours.
Preheat the oven to 350°F and line the baking sheets with parchment paper.
Scoop the cold dough into 3-ounce balls and place them on the prepared baking sheets, leaving space between each one.
Bake for 12 to 14 minutes, until the edges are golden.
The second the cookies come out of the oven, press a rounded 1-tablespoon measuring spoon deeply into the center of each cookie to create a well.
Let the cookies firm up on the baking sheets for 5 minutes, then transfer them to a wire rack.
Add the butter, dark brown sugar, heavy cream, and corn syrup to a saucepan. Cook over medium heat until the butter has melted and the ingredients are combined.
Bring the mixture to a boil and let it bubble for only 30 seconds.
Remove the saucepan from the heat and stir in the chopped pecans, vanilla extract, and fine sea salt.
Spoon generous mounds of the warm pecan topping into the cooled cookie wells.
Let the topping cool and set for about 30 minutes.
Melt the chocolate chips in a microwave safe bowl in 30 second intervils and drizzle the chocolate over the cookies.