Pre-heat oven to 350. Grease a 9x13 pyrex pan, or line with parchment paper.

Mix canola oil and butter, add cocoa and stir until well blended. Beat the eggs with a mixer. Add sugar and vanilla, beat well. Add the chocolate mixture and beat to combine. Slowly add in the flour and salt. Stir in chocolate chips.

Spread half of the brownie mixture evenly in pan, it will make a very thin layer. Bake at 350 degrees for about 5 minutes (if you want a super fudgy almost doughy brownie skip baking the bottom brownie layer and just bake the whole pan at once).

While the brownies bake make the filling.

Mix Karo syrup and peanut butter together in large saucepan. Heat almost to a boil but be careful not to burn. Stir to combine the ingredients. Turn off the heat and stir in the vanilla. Then add and mix in cornflakes. You may also just warm together the karo syrup and peanut butter together in the microwave until smooth and melted, then stir in the vanilla. Then just pour over the corn flakes and mix.

Drop about 3/4 of the cornflake mixture evenly over the brownies, save the remaining cornflake mixture for later.

Spread the remaining brownie batter over top the the cornflakes. This is going to be hard since the batter is so thick and you likely will not be able to cover the whole top of the cornflakes. This is ok and they will bake and spread a little in the oven. Bake for 15 to 20 (add 5 minutes if you did not pre-bake the bottom layer), but watch closely.

Remove from the oven and immediately top with the Hershey squares. Place a piece of foil over the brownies and allow the chocolate to melt, about 5 minutes. Once the chocolate is melted, smooth it out so that it covers the whole pan and then top with clusters of the remaining peanut butter cereal, gently pressing the clusters into the melted chocolate to adhere. Drizzle with melted chocolate if desired. Allow to cool completely before serving or refrigerate for 2 hours. Brownies can be kept at room temperature (if your house is cool) or in the fridge.