Preheat oven to 350 degrees. Line a 9 x 13 pan with parchment paper and spray with cooking spray. Set aside.

In a large bowl or the bowl of a stand mixer, add butter, sugar and cocoa powder and beat on medium speed until combined, about 2 minutes. Add eggs one at a time until combined. Add in vanilla and beat until mixed in.

In a bowl whisk together the flour, salt, baking powder and espresso. Slowly pour into the butter mixture and stir until batter in just combined. Fold in nuts, chocolate chips, and caramel bits until combined.

Pour batter evenly into prepared pan and bake for 30 to 35 minutes. Let pan cool on a wire rack for 10 to 15 minutes.

In bowl or stand mixer, beat butter, cocoa, corn syrup, and vanilla until blended and fluffy, about 1 minute. Add in powdered sugar and 2 tablespoons milk and beat until smooth. Add in additional milk if needed to reach desired spreading consistency.

Once brownies have mostly cooled, spread on frosting. Sprinkle with chocolate chips, chopped nuts and drizzle with caramel sauce