Preheat oven to 350F. Line an 8 x 8″ baking pan with foil or parchment paper and spray with baking spray, set aside.

In a medium pan melt the butter and the condensed milk together. Stir in the chocolate chips and continue to stir until the chips are melted and the mixture is smooth. Remove from the heat and let the chocolate mixture come to room temperature.

Sift the cocoa powder, all-purpose flour, espresso powder and salt into a bowl, set aside.

In the bowl of a stand mixer fitted with a paddle attachment beat the eggs, egg yolk, brown sugar and granulated sugar on medium-high speed for about 3 minutes or until the mixture lightens in color. Add the vanilla extract and beat until incorporated, about 20 seconds.

Add the cooled chocolate mixture and stir with a rubber spatula. Then add the sifted dry ingredients, stir until just combined. Do not over stir.

Pour the batter into the prepared baking pan, smooth the top. Bake for 45-50 minutes, or until a toothpick inserted in the center comes out almost clean. It is ok to have a few crumbs cling to the toothpick. Do not over bake!

Cool the brownies completely, then remove from the pan and cut into squares.