Preheat the oven to 180°C.
Whisk egg whites in a bowl until stiff peaks form.
Gradually whisk in the sugar one tablespoon at a time.
Fold in the chocolate, cocoa powder, vinegar, and nuts gently.
Spoon small mounds of the mixture onto a lined baking tray.
Decrease the oven temperature to 150°C and bake for 45 to 50 minutes.
Mix the cream, vanilla seeds, and sugar in a clean bowl for the filling.
Melt the chocolate hazelnut spread, butter, cream, and liqueur in a pan over low heat.
Sandwich the filling between two meringues and top with sauce to serve.