Preparation: Begin by preheating the oven to a temperature of 375°F. Thoroughly spray a 9x13 baking pan with a non-stick baking spray.

Mixing: In a large mixing bowl, cream together the softened unsalted butter, brown sugar, and granulated sugar until a smooth consistency is achieved. Subsequently, incorporate the large egg, vanilla extract, and either the caramel coffee creamer or milk into the mixture, ensuring thorough mixing.

Dry Ingredients: In a separate bowl, sift together the all-purpose flour, dark cocoa powder, baking powder, and salt. Once sifted, methodically combine the dry ingredients with the previously prepared butter mixture, ensuring that a consistent dough is formed.

Baking: Transfer the dough to the pre-sprayed baking pan, ensuring that it is evenly spread across the entire surface of the pan. Place the pan into the preheated oven and bake for approximately 14-15 minutes, taking care to avoid over-baking. Once baked, remove the pan from the oven and allow the contents to cool to room temperature.

Finishing Touches: Once cooled, uniformly spread the Salted Caramel Frosting over the surface. If desired, a sprinkling of coarse ground sea salt can be added for enhanced flavor. Conclude by dividing the contents into 24 individual bars and store them in an airtight container for optimum freshness.