Add the cottage cheese, confectioners’ sugar, and cocoa powder to a blender or food processor. Process until completely smooth and relatively thin in consistency, forming a creamy chocolate mousse base.
Transfer the blended mousse to a freezer-safe serving dish. Freeze for 1–2 hours, stirring the mixture once at the halfway point to encourage an even texture and help minimize the formation of ice crystals.
While the mousse is chilling, place the dark chocolate in a microwave-safe container. Microwave it in short intervals, stirring approximately every 10 seconds, until the chocolate is fully melted, glossy, and smooth. Take care not to overheat it.
Remove the set mousse from the freezer and pour the melted dark chocolate evenly over the surface. If desired, scatter a small amount of sea salt over the chocolate for a sweet-and-salty contrast. Serve once assembled.