Make the Brownie Batter:
Preheat oven to 350F. Line an 8-inch square pan with aluminum foil leaving overhang and spray with cooking spray, or grease and flour the pan; set aside.
In a large microwave-safe bowl, add the butter, chocolate, and heat on high power to melt, about 2 minutes. Stop to check and stir after 1 minute. Heat in 15-second increments until chocolate has melted and mixture can be stirred smooth. Allow mixture to cool momentarily before adding the eggs so they don’t scramble.
Add the eggs, sugar, vanilla, optional coffee, optional espresso granules (neither make brownies taste like coffee and both enhance and round out the chocolate flavor), optional salt, and whisk vigorously to combine.
Add the flour, most of the diced Oreos, reserving a small handful to be sprinkled on top, and stir until smooth and combined without overmixing.
Turn half the batter out into prepared pan, smoothing the top lightly with a spatula as necessary; set aside while you make the Cream Cheese Filling.
Make the Cream Cheese Filling:
In a medium bowl, add the cream cheese, confectioners’ sugar, vanilla, and beat with an electric hand mixer until smooth and combined, or whisk vigorously to combine.
Turn filling out over brownie base to create an even, smooth, flat layer. Take your time spreading the cream cheese over all areas with a knife or spatula. Tip – Rather than allowing the cream cheese to ‘plop’ out of the mixing bowl in one area of the pan, try to dollop it out in small ‘clumps’, which makes spreading it neatly much easier.
Turn out remaining brownie batter over cream cheese layer and take your times spreading the batter over bare patches and into the corners. Using the Tip from Step 7 is helpful here, too.
Evenly sprinkle the reserved handful of Oreos over the top.
Bake for about 30 minutes, or until center has just set and is no longer glossy.
Allow brownies to cool in pan on top of a wire rack for at least 2 hours. Then cover with a sheet of foil to prevent fridge smells, and place pan in fridge for at least 2 hours, or until sufficiently chilled for slicing. Do not rush the cooling process because the cream cheese will ooze everywhere and the brownies need time to really set up before slicing.
Lift brownies out using foil overhang, slice, and serve. Brownies will keep airtight in the fridge for up to 10 days, or in the freezer for up to 6 months. I prefer these brownies slightly chilled and store them in the fridge.