Preheat the oven to 350°F. Line an 8-inch square baking pan with parchment paper.
In a small bowl, stir the espresso powder and hot water together until dissolved.
In a large mixing bowl, whisk the melted butter, granulated sugar, and brown sugar for about 2 minutes until glossy and well combined.
Whisk in the eggs and egg yolk one at a time. Stir in the vanilla extract and dissolved espresso mixture.
Add the cocoa powder and salt and whisk until smooth.
Fold in the flour just until combined. Gently stir in the white chocolate chips.
Spread the batter evenly into the prepared pan.
Bake for 30 to 34 minutes, or until the edges are set and a toothpick inserted near the center comes out with a few moist crumbs attached.
Let the brownies cool completely in the pan.
To make the glaze, whisk together the powdered sugar, heavy cream, vanilla extract, and espresso powder until smooth.
Remove the brownies from the pan and drizzle the glaze over the top.
Finish with the caramel sauce and a light sprinkle of flaky sea salt.
Chill for 15 to 20 minutes before slicing into squares.