Preheat your oven to 350°F (175°C) and prepare a 9x13 inch baking dish by greasing it well.

In a medium saucepan, combine 2 sticks of unsalted butter and 3 double shots of espresso over low to medium heat until melted.

Remove from heat and add dark chocolate and cocoa powder, stirring gently until melted and smooth.

In a large bowl, whisk together light brown sugar, bourbon vanilla extract, and a pinch of kosher salt until fully combined.

Pour the warm chocolate and espresso mixture into the dry ingredients and fold until just combined.

Whisk in 3 large eggs and 2 yolks until smooth and glossy.

Gently fold in the flour and baking soda until just combined.

Pour the batter into the greased baking dish and smooth the top. Bake for 22-25 minutes.

Once baked, cool the cake in the pan for 10 minutes, then transfer to a wire rack to cool completely.

For the frosting, melt 1.5 sticks of unsalted butter in a saucepan until golden brown and nutty.

Combine cooled browned butter with powdered sugar and heavy cream in a stand mixer and whisk until smooth.

Generously spread the brown butter frosting over the cooled cake.