Preheat oven to 180ºC (350ºF) fan-forced. Line a square 9-inch x 9-inch (22cm x 22cm) baking tin with parchment paper and set aside.
Melt butter and set aside for 5 minutes to cool down or until it’s just warm, not hot.
Prepare a large mixing bowl, using either electric hand beaters or a stand mixer with the paddle attached.
In the mixing bowl, pour in cooled melted butter along with the eggs, sugar and vanilla. Beat on medium speed for 2 minutes until well combined.
With the beater running on low-medium speed, slowly drizzle in the olive oil in a steady stream to emulsify, about 1 minute in total.
Sift over flour and cocoa powder. Add the salt. Beat on low-medium speed until incorporated, ensuring not to over-beat.
Pour batter into the lined tin and spread out evenly.
Bake for 18-22 minutes or until a toothpick inserted into the middle comes out with some moist crumbs, not completely clean. Slightly under-baking will create a fudgy texture.
Remove from oven and allow to cool in tin for 10 minutes.
Carefully pull brownie out from the tin and transfer to a wire rack, leaving the parchment paper intact as it will still be soft and delicate to handle.
Allow the brownie to cool completely before pouring over the caramel, this may take a couple hours.
Once the brownie has cooled, either gently pick it up and place it back into the baking pan or leave it on the rack with the paper underneath.
Pour refrigerated caramel over the brownie and spread it out with a rubber spatula or the back of a spoon.
Sit at room temperature until caramel firms up slightly or refrigerate for 15-20 minutes until set. Note: Caramel won’t harden, it will remain soft but will firm up slightly in the fridge.
Cut into squares and enjoy!