Preheat your oven to 350°F (175°C).
Line your 9x13-inch baking pan with parchment paper.
In a large mixing bowl, combine the chocolate cake mix, softened butter, and egg. Use an electric mixer to beat until well combined and smooth.
Pour half of the chocolate batter into the prepared baking pan and spread it evenly.
Place a layer of shortbread cookies on top of the chocolate batter.
In a separate bowl, combine the toasted coconut and caramel bits. Sprinkle this mixture over the layer of shortbread cookies.
Pour the remaining chocolate batter over the coconut and caramel layer and spread it gently.
Bake for 25-30 minutes, until a toothpick comes out with a few moist crumbs.
Remove from the oven and sprinkle chocolate chips on top.
Drizzle sweetened condensed milk over the melted chocolate chips.
Let cool for at least 30 minutes, then lift out and cut into squares.