Preheat oven to 350 with the rack in the lowest position
Line a 9x13 pan with two layers of tin foil, with one set of long edges hanging out over the 9-in sides so that you can easily remove the brownie from the pan
Spray foil lined pan with baking spray
Whisk cocoa powder and boiling water until smooth
Add chopped unsweetened chocolate until melted and smooth
Add melted butter, oil, eggs and egg yolks and whisk again
Whisk in sugar and vanilla
Using a spatula, add flour and salt to this bowl of chocolate glory
Add chips and fold gently
Pour batter evenly into pan
Bake for 35 minutes or until knife comes out relatively clean - don't be fooled by the melting chips!
Lift the brownie from the pan and cool completely on a wire rack.
[Optional: with a long knife, remove the crispy 1/4 inch around the edge and reserve for ice cream topping or toasting as biscotti. I think I must be the only person in the world who does not like crispy edges on a chewy brownie...but who knows?]
Slice brownie into squares.