Prepare and bake the cake according to package directions, using a 13x 9 – inch cake pan. Let the cake cool for 15 to 20 minutes. Using the round end of a wooden spoon, poke holes in the cake every 1/2 inch to 1 inch.
Combine the sweetened condensed milk and caramel topping in a medium bowl. Whisk briskly for 1 minute or until the mixture is well combined. Evenly pour over the poked cake, filling the holes as much as possible. Place the cake in the refrigerator for about 1 hour.
Remove the cake from the refrigerator. Spread the chocolate frosting over the cake.
Use the back of a spoon or an offset spatula to spread it evenly. Sprinkle the chopped pecans and mini chocolate chips over the frosting. Drizzle with additional caramel sauce. Refrigerate for at least 2 hours before serving.
Store covered in the refrigerator.
In a mixing bowl, stir together melted butter and cocoa until dissolved. Stir in 1/2 cup of powdered sugar. Stir in milk and vanilla.
Add remaining powdered sugar and beat until it’s smooth and creamy.
Add additional milk or powdered sugar if necessary to create an easy to spread frosting.