Preheat oven to 350° and prepare a baking dish with parchment paper and sprayed with non-stick spray. The parchment paper or foil will help to remove brownies after baking.
In a small bowl, whisk together the flour and salt and set aside. Melt butter.
In a large bowl, combine cocoa powder with espresso powder and pour over boiling water. Whisk until smooth.
Add in bittersweet mini chips and stir until melted and smooth.
Next, add olive oil and melted butter. Whisk together until well combined. If mixture appears slightly curdled it's ok.
Whisk in eggs, egg yolks and vanilla extract until well combined.
Then stir until sugar, followed by flour, scraping down sides of bowl to ensure no flour pockets remain. Fold in semi sweet chocolate chips.
Transfer mixture to prepared pan and bake for 30-35 minutes if pan is 9x13. It will be closer to 40-45 minutes if you use a smaller pan, like 8x8, and brownies are thicker. Test for doneness by inserting a toothpick or knife into center. Thick, moist crumbs should appear. If in doubt, under bake brownies slightly. Let cool for 30 minutes in pan. If you use a glass baking pan, be sure to remove after 10 minutes since glass hold heats much longer than other baking materials. Let cool completely on a wire rack. Then cut and serve. Store for up to five days in an air tight container.