Preheat oven to 350°F (175°C) and line a muffin tin with cupcake liners.
Prepare chocolate cake mix according to package instructions using eggs, oil, and water.
Fill each cupcake liner about 2/3 full and place half a mini Twix bar in the center.
Bake for 18–20 minutes or until a toothpick inserted comes out clean. Let cool completely.
In a large bowl, beat softened butter until fluffy.
Gradually add powdered sugar, heavy cream, caramel sauce, and salt. Beat until smooth.
Frost cooled cupcakes using a piping bag or spatula.
Top with chopped Twix pieces and a drizzle of caramel sauce.