1. In a saucepan combine the sugar, egg yolks and 1/2 cup of the heavy cream. Whisk constantly over low heat. Continue to whisk, making sure to reach the inner edges of the pan, until an inserted thermometer reads 140F.

2. Once the custard has reached 140F, continue to cook for 3 1/2 minutes. (Be careful to maintain this temperature, do not let it increase.)

3. After 3 1/2 minutes, reduce heat and add chocolate. Stir until melted.

4. Remove from heat and add rum. Mix well. Mixture will be quite thick. Transfer to a cool bowl.

5. In an electric mixer beat the remaining 1 1/2 cups of cream until stiff.

6. Check with your finger that chocolate is at room temperature.

7. Fold one large spoonful of the whipped cream into the chocolate mixture to lighten it. Add the remaining cream. Fold gently only until thoroughly blended.

8. Spoon into serving dish. Refrigerate until set, approximately 4 hours.