Grease an 8 inch cast iron skillet with butter and set aside. Preheat the oven to 350℉.
In a medium sized saucepan over medium heat, melt the butter. Once melted, keep cooking and the butter will begin to sizzle and foam. Keep cooking, stirring occasionally until the butter starts to brown. Once browned, remove from the heat and pour into a large mixing bowl. Let it cool for 5 minutes before continuing.
To the slightly cooled brown butter, whisk in the brown sugar and granulated sugar. Add the eggs, bourbon, espresso powder, and vanilla extract and whisk until combined. Add in the flour, cinnamon, cardamom, ginger, cornstarch, baking soda, and salt and use a large wooden spoon or spatula to fold the mixture together into a smooth dough. Finally, fold in the chocolate chunks.
Spread the dough into the previously prepared skillet and bake for 20-25 minutes or until the top and sides are browned but the center is still gooey. Let the cookie cool for 10 minutes before serving warm with a sprinkle of flakey sea salt and a scoop of ice cream.
