How to Make It
Preheat oven to 375°F. In a medium saucepan, combine the butter and 3 ounces chocolate (about ½ cup) over medium-low heat until melted, stirring often, 2 to 3 minutes. Remove from heat and stir in sugar and vanilla. Add the cocoa powder and a pinch of salt; stir to combine.
Coat a 12-cup standard muffin tin with nonstick cooking spray. Unroll one can of crescent roll dough on a lightly-floured piece of parchment paper. Pinch together any seams so that you have a smooth rectangle with no holes. Flip the dough over and repeat.
Spread half the chocolate mixture over the dough. Top with half of the remaining chopped chocolate and a pinch of flaky salt. Starting with the short end nearest to you, roll the dough into a log and place seam side down. Slice crosswise into six rounds. Place cut side up in the prepared muffin tin. Repeat with second can of dough, chocolate mixture, and remaining chopped chocolate.
Brush the tops of the crescent rounds with the beaten egg. Bake until the buns are puffed and golden brown, 14 to 16 minutes. Serve warm.