Preheat the oven to 325°F. Spray a 9X9-inch pan with baking nonstick spray. Line the bottom and two sides of the pan with parchment paper and spray again.
In a medium bowl, mix the flour, cocoa powder, cornstarch, and salt.
¾ cup All-purpose flour, 1 cup Unsweetened cocoa powder, 1 tablespoon Cornstarch, 1 teaspoon Salt
Using a mixer with a whisk attachment, beat the sugar, eggs, and egg yolk on high speed for 5 minutes. It will become pale and light in color.
2 cups White granulated sugar, 3 Large eggs, 1 Egg yolk
Add the oil, melted butter, and vanilla and mix on until combined. Add in the dry ingredients and mix on low until combined.
½ cup Oil, ½ cup Unsalted butter, 1 teaspoon Pure vanilla extract
Take off the mixer and use a rubber spatula to scrape the bowl, mix in the chocolate chips and chopped pecans.
1 ⅓ cup Semi-sweet chocolate chips, ½ cup Chopped pecans
Pour brownie batter into the pan. Bake for 45-55 minutes until edges are set and the middle is only slightly underdone. If you stick a toothpick in and it has batter on it, bake for another 5-10 minutes. If it comes out with crumbs, it is ready.
Cool the brownies in the pan on a cooling rack completely before taking them out of the pan. Make the caramel while the brownies bake.