Using a double boiler, combine chocolate, milk and cream. Simmer until chocolate melts.
Meanwhile, melt butter in the microwave. Stir into the chocolate.
Using an electric mixer, combine the egg whites and salt. Beat until stiff peaks form.
Beat egg whites and sugar until light and fluffy.
Using a rubber spatula, fold in the flour. At this point, it will be very clumpy.
Add chocolate and fold in until thoroughly combined.
Finally, fold in the egg yolks. No matter how much I mixed, the batter was still a little clumpy. Turn the mixer back on and beat for about 3-4 minutes until thoroughly combined and try to get as smooth as possible.
Pass the batter through a sieve into a saucepan. On medium heat, simmer for about 5 minutes, stirring constantly.
Serve warm, garnished with pistacchios.