Preheat oven to 350°F (177°C) and line a baking pan with parchment paper.
Whisk together melted butter, sugar, and brown sugar until smooth.
Beat in eggs, vanilla, and espresso, mixing until fully combined.
In a separate bowl, sift flour, cocoa powder, salt, and baking powder.
Gradually fold dry ingredients into wet ingredients until just combined.
Stir in dark chocolate chips and pour batter into the prepared pan.
For the caramel, heat sugar and water in a saucepan over medium heat.
Cook until the mixture turns deep amber, then slowly stir in heavy cream.
Remove from heat, add butter and salt, and whisk until smooth.
Drizzle caramel over brownie batter and swirl it in using a knife.
Bake for 35 minutes or until the center is just set.
Let brownies cool completely before cutting (yes, this is torture).
Slice, serve, and lose all willpower.