Preheat the oven to 350 F. Layer a 9x13 pan with parchment paper (if you cannot get parchment paper because you are at the beach, used lightly buttered foil). Set aside.
Whisk together the flour, baking powder and salt in a medium sized bowl. Set aside.
Melt the butter in the microwave on medium-low power bursts. When it is melted, whisk in the oil. Whisk in the espresso powder.
Add the sugars and extracts and whisk in. Whisk quite briskly to emulsify the sugars into the fat.
Whisk in the eggs, one at a time.
Switch to a rubber spatula and stir in 2/3 of the flour mixture. Stir the remaining third in, but before it is completely incorporated, add the chocolate chips. Mix the chips in evenly, until all flour is incorporated.
Scrape 2/3 of the cookie dough into the prepared baking pan. Smooth the dough evenly into pan.
If your dulce de leche is in a glass jar, you can briefly heat it to make spreading it easier. Dollop it in blobs over the cookie dough and spread it evenly over the dough. Scrape the remaining cookie dough over the dulce de leche and spread it out. Do not worry if some dulce de leche seeps through.
Sprinkle the top evenly with a good quality coarse or flaky sea salt--or just use kosher salt if that is all you can get!
Place in the oven and reduce the heat to 330 F. Bake for 30 minutes, or until set and beginning to crack.
Let cool completely before slicing.