Preheat the oven to 350 degrees Fahrenheit (175 degrees Celsius). Line baking sheets with parchment paper or silicone mats.

In a mixing bowl, whisk together the 2 ½ cups of all-purpose flour, cornstarch, baking soda, and sea salt. Set aside.

In another bowl, cream together the softened butter and 1 cup of brown sugar, sugar, until light and fluffy. Add the egg, egg yolk, and vanilla extract, and mix until well combined. Making sure to scape down the bowl.

Gradually add the dry ingredient mixture to the wet ingredients, mixing until a cookie dough forms. Set aside the dough while you prepare the pecan topping. Do not overmix.

For the pecan topping, melt 5 tablespoons of unsalted butter in a saucepan over medium heat. Stir in ½ cup of dark brown sugar, maple syrup, chopped pecans, and a pinch of salt. Cook for a few minutes, stirring occasionally, until the mixture thickens slightly. Add heavy cream and vanilla and cook for an additional 1 minute. Remove from heat, and let it cool.

Take 1 large ice cream scoop portions of the cookie dough (¼ cup), and roll them into balls. Place them on the prepared baking sheets, leaving space between each cookie. Refrigerate overnight or freeze for 1-2 hours.

Once ready to bake, pop the cookies in the oven. Bake for 12-13 minutes or until the edges are golden brown.

Immediately take the back of a measure spoon, and press down the center of the cookie to create a little well.

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

Top with a a large tablespoon full of the pecan mixture, and sprinkle with flakey sea salt.