3/4 cup (1 1/2 sticks) unsalted butter, room temperature or almost melted
3/4 cup granulated white sugar
3/4 cup packed light brown sugar
1/4 teaspoon salt
2 tablespoons milk or cream
1 1/2 teaspoons vanilla extract or vanilla bean paste
1 cup all-purpose flour
1 cup miniature chocolate chips
additional miniature chocolate chips, if desired (to garnish the top)
PREPARE THE BROWNIE LAYER-
Preheat the oven to 350 degrees F. Spray a 9×9-inch pan with nonstick spray, then line with a strip of parchment paper so that it covers the bottom and comes up two sides of the pan. Spray the parchment with nonstick spray too.
In a microwave safe bowl (or in the top of a double boiler or pan set on top of a pan of simmering water), microwave in 30 second bursts to melt butter and chocolate chips together until all is melted and smooth. Whisk in the sugars, then whisk in the eggs, vanilla and salt. Sift flour into the bowl and stir that in too. Scrape the brownie batter into the prepared pan. Bake for 25 to 30 minutes, or until the brownie layer is cooked through (toothpick inserted into the center comes out clean). Place the pan of brownies in the refrigerator to speed up the cooling process (or cool at room temperature and add the cookie dough layer later).
PREPARE THE COOKIE DOUGH LAYER:
In a large bowl, use an electric mixer to combine the butter, sugars and salt until soft and creamy (1 to 2 minutes). Mix in the milk and vanilla. Sprinkle in the flour and mix in until combined. Stir in the 1 cup of chocolate chips. Scoop the cookie dough onto the top of the brownies and spread onto the brownie layer. I find that it’s easiest to do this if the brownie layer is chilled and firm. Wet your hands or spray them with nonstick spray and pat the cookie dough on top in a even layer. Sprinkle additional chocolate chips on top to create a nicer, visual appearance. For easy, clean cutting, chill the brownies (wrap the brownies with plastic wrap and chill until firm- 1 to 2 hours or up to 2 days).
Cut the brownies: Run a knife along the sides of the brownie pan and then use the parchment paper to lift the brownies from the pan and onto a cutting board. Slice the brownies with a sharp knife, wiping the knife with a paper towel between cuts. If you’d like all of your slices of brownies to look clean-cut without edges, use the knife to cut the sides of the brownies off before cutting pieces. Keep brownies slices covered and chilled until ready to serve.