TO MAKE THE CAKE: melt the chocolate in a small saucepan over very low heat. Add quarter cup of sugar and the butter and stir until melted. Whisk in the egg yolks. Cook stirring constantly until mixture reaches 70ºC on a candy thermometer. Set aside to cool. In a mixing bowl, beat the egg whites until stiff. Add the remaining sugar and beat until glossy. Whisk one third of the egg whites into the chocolate mixture. Fold in the remaining whites. Rinse 4 4 oz. heart shaped molds or ramekins with water; DO NOT DRY. Divide the chocolate mixture among the molds. Refrigerate for 24 hours. TO MAKE THE SAUCE: Remove as much skin as possible from the pistachios. Rinse quickly with boiling water, drain and then remove as much of the remaining skin as possible. Place the nuts in a food processor and pulse until ground. Add one third cup of sugar and the egg white and process until mixture forms a paste. Place 3 T of the pistachio paste in a medium sized saucepan (save the rest for another use). Add the milk and bring mixture to a boil over medium heat. Remove from the heat and let steep for 5 minutes. Strain through a fine mesh sieve into another medium size saucepan. Set aside. Whisk together the egg yolks and the remaining sugar until thick and light. Whisk in half the strained milk; then whisk the mixture back into the remaining milk. Cook the sauce over low heat, stirring constantly until thick enough to coat the back of a spoon; do not let the mixture come to a boil. Refrigerate for 24 hours. TO SERVE: Spoon a pool of the sauce onto the center of each of 4 plates. Run the tip of a small knife around the inside edge of the molds. Dip them briefly into hot water and invert them onto the plates. ----