Preheat the oven to 350°F and line a cupcake pan with liners.
In a large bowl, mix the cake mix, eggs, sour cream, oil, milk, cocoa powder, and vanilla until smooth. Fill liners about two-thirds full and bake for 18 to 22 minutes, until a toothpick comes out clean. Let cool completely.
Once cooled, core the center of each cupcake without going all the way through. Spoon caramel into the center, filling almost to the top, then gently replace the cake piece.
For the frosting, beat the butter until smooth. Add powdered sugar, cocoa powder, vanilla, and heavy cream, mixing until creamy and fluffy. Add more cream if needed to reach a soft, pipeable consistency.
Pipe or spread frosting over each cupcake, covering the filled center. Sprinkle lightly with coarse sea salt, top with a chocolate-covered pretzel, and finish with a light mist of gold glitter dust. Drizzle with extra caramel if desired.