Preheat the oven to 350°F. Spray a 9X9- inch pan with baking nonstick spray. Line the bottom and 2 sides of the pan with parchment paper and spray again.
In a medium bowl, sift the flour and cocoa powder. Mix in the cornstarch and salt and set aside.
1 cup All-purpose flour, 1 cup Unsweetened cocoa powder, 1 TBSP Cornstarch, 1 tsp Salt
Using a mixer with a whisk attachment, beat the sugar, powdered sugar, eggs, and egg yolk on high speed for 5 minutes. It will become pale in color. Stir in the vanilla, oil, and melted butter and mix on low until just combined.
1 1/2 cups White granulated sugar, 3 Large eggs, 1 Egg yolk, 2 tsp Pure vanilla extract, 1/2 cup Oil, 1/2 cup Unsalted butter, 1/2 cup Powdered sugar
Add in the dry ingredients and mix on low until just combined. Take off the mixer. Pour in the chocolate chips and chopped snickers. Use a rubber spatula to fold in the mix ins.
1 cup Semi-sweet chocolate chips, 1 cup Chopped Snickers
Pour the brownie batter into the pan. Use a teaspoon to dollop salted caramel on top of the brownie batter. I used 12 teaspoons. Use a butter knife to very lightly swirl it on top.
Bake for 40-50 minutes. Bake until the edges are set and the middle is under baked. If you stick in a toothpick it should come out with fudgy brownie on it. If it is pure brownie batter, bake for another 5 minutes and check again.
Top the brownies immediately with extra chopped Snickers. Let the brownies cool on a cooling rack. Take the bottom of a wooden spoon and poke holes into the brownies. The caramel will melt and cause holes on top of the brownies. Pour extra caramel on top of the brownies. It will sink in the holes!