Preheat the oven to 350°F (175°C) and prepare a 9x13-inch metal cake pan by lining it with parchment paper and lightly spraying it with cooking spray.

Melt a cup of salted butter in a saucepan over low heat, combine it with granulated sugar, stirring until smooth, then remove from heat and let cool for 5 minutes.

Whisk in oil and vanilla extract. Add eggs one at a time, mixing well after each addition.

Sift flour, cocoa powder, and salt into the mixture, then mix until just combined. Gently fold in mini chocolate chips.

Pour the brownie batter into the prepared pan and bake for 20 minutes, until a toothpick comes out with a few moist crumbs.

In a saucepan over medium heat, combine brown sugar, butter, and corn syrup. Stir until smooth and boiling.

In a separate bowl, mix water with cornstarch, then add to the boiling sugar mixture along with vanilla and salt, stirring well.

Beat eggs until frothy, then slowly incorporate the sugar mixture. Fold in chopped pecan pieces and halves.

Pour the pecan mixture over the already baked brownies and return to the oven for another 22-25 minutes, until the center is slightly jiggly.

Allow the brownies to cool for 6 hours before slicing into squares for serving.