01 -
Preheat oven to 350°F and coat a 9×13 inch baking pan with non-stick spray or line with parchment paper extending the sides for easy removal.
02 -
In a stand mixer with paddle attachment or using a hand mixer, cream together unsalted butter and granulated sugar until smooth and fluffy.
03 -
Add eggs and vanilla extract to the creamed mixture. Continue mixing and scrape down bowl sides as needed until fully combined.
04 -
In a separate bowl, whisk together cocoa powder, all-purpose flour, and salt.
05 -
On low speed, alternate adding the dry mixture and milk to the wet ingredients: start with dry ingredients, then add half the milk, more dry ingredients, the remaining milk, and finish with the rest of the dry mixture. Mix until just incorporated.
06 -
Pour batter into prepared pan, spread evenly, and bake in the center of the oven for 30 minutes. Allow to cool for 20–30 minutes; brownies should remain slightly warm for frosting.
07 -
In a saucepan over medium-high heat, combine butter, milk, and granulated sugar. Bring to a boil and continue boiling for 1 minute. Remove from heat, add salt and milk chocolate chips, and whisk vigorously until smooth.
08 -
Immediately pour hot frosting over the warm brownies, spreading quickly with an offset spatula before it begins to set. Allow to rest for at least 1 hour before slicing.