1. Break the chocolate into small pieces in a bowl. Melt the chocolate in the microwave.
2. Add the salt and butter in small cubes, whisking until the mixture is homogeneous.
3. Separate the egg whites from the yolks. Beat the egg whites until stiff peaks form.
4. Add the egg yolks to the melted chocolate and mix well.
5. Using a spatula, gently fold in the beaten egg whites. Refrigerate for 3 hours.
6. To serve, dip a tablespoon in boiling water for 10 seconds and make quenelles with the chocolate mixture.
7. Serve with a chocolate sauce.