Pre-heat oven to 350 degrees
Coat a non-stick 9 x 9 -inch baking pan with pan spray and line with parchment paper. Set aside.
Measure both sugar measurements into a medium bowl. Whisk together. Set aside.
In a microwave, melt the butter and chocolate together in a glass bowl on low heat for 30 seconds. Stir and microwave for another 30 seconds. Continue until chocolate is completely melted and mixture is very warm.
Add the melted butter and chocolate mixture to the sugar mixture. Stir by hand for approximatelty one minute to help dissolve the sugar.
Add the vanilla, oil, eggs, and egg yolk. Stir the mixture until it is silky and thick, about 3 minutes. This is how the shiny tops are formed so be sure to stir for the full 3 minutes.
Stir in the flour, cocoa powder, baking soda and salt. Mix until you can no longer see any dry flour spots.
Pour the batter into the prepared 9 x 9- inch pan. Bake at 350 degrees for 35-40 minutes or until the toothpick comes out clean, but moist.
.Allow the brownies to cool completely before cutting into 9 equal pieces.