1In a saucepan, melt the butter over medium heat. Continue cooking until it foams, turns golden brown, and smells nutty (3–5 min). Remove from heat and cool slightly.
2In a bowl, whisk browned butter with brown sugar and granulated sugar.
3Add egg and vanilla, whisk until smooth.
4Fold in flour just until combined.
5Stir in chocolate chips.
6Whisk in eggs and brown sugar for the brownie layer until light.
7Add brown butter and melted chocolate and whisk until combined.
8Fold in cocoa powder, flour, salt, and instant coffee.
9Add chopped chocolate to the brownie batter.
10Spread the cookie dough evenly into the prepared pan.
11Pour brownie batter on top of the cookie dough layer. Spread evenly.
12Tap the pan gently on the counter to release air bubbles.
13Bake for 30–35 minutes. The top should look set but a toothpick inserted in the center comes out with a few moist crumbs (not wet batter).