In a small bowl, add ½ cup butter and microwave until melted.
Add in 1 Tbsp hot chocolate mix and 1 cup roughly chopped chocolate. It will partially melt, it's fine if there are still chunks.
Using a spoon, spread the chocolate filling over the flattened dough, smear into a roughly even layer. Oil your hands and then fold the dough into thirds. Turn so the long side matches the long side of the pan.
Allow to rise 1½ - 4 hours uncovered in a warm, dry spot.