Preheat oven to 350°F. Line two large baking sheets with parchment paper or a silicone baking mats, set aside. (Unless you plan on chilling the dough for best texture results, then skip this step for now.)
In a large bowl, whisk together the flour, brown sugar, granulated sugar, baking soda, cornstarch, salt and cinnamon.
Add butter, combine with a spatula or with a handheld mixer until crumbly. Add eggs and vanilla extract and beat until well combined. Fold in toffee chips, caramel squares and pecans. (Optional: reserve a few toffee chips, caramel squares and pecans to top cookie dough with for a prettier presentation.)
Optional: Cover and chill the dough in the refrigerator for 2 hours, or up to 24 hours. Allowing the dough to rest will help the flour to absorb better, so the thicker and chewier the final texture will be.
Roll two heaping tablespoons of cookie dough into a ball and place on prepared baking sheet leaving 2-inches per cookie for spreading. (If you reserved extra toppings, place them on top of cookie dough now.)
Bake for 12 minutes, or until the edges of cookies are set and golden brown. Remove from oven and immediately sprinkle with flaky sea salt, to taste.
Let cookies cool and set up for 10 minutes on baking sheet before transferring to a wire rack to cool completely.
