Preheat oven to 350.

Line a 9x13 pan with wide heavy duty foil, leaving a couple inches over the edge (to pull brownies out after baking). Spray the foil with cooking spray.

Boil a pot of water. Meanwhile, whisk cocoa and espresso powder in bowl. Measure boiling water, then pour into cocoa espresso mixture, and whisk until blended.

Add semi sweet chocolate and whisk until melted.

Stir in melted butter and oil. So now it is time to add in the eggs, egg yolks and vanilla. Continue to stir until smooth. Add in sugar and mix until smooth. 

Whisk  in flour, and salt until incorporated.  Stir in milk chocolate chips.

Scrape batter into foil lined pan. Bake 35 minutes, turning pan half way thru. Test with toothpick, watching for  a few moist crumbs attached. 

Transfer pan to wire rack and let cool completely, about 1 hour. Remove from pan using foil liner to lift brownies out of pan. Cut when cooled.