In 2-quart saucepan, heat 1 cup of the whipping cream over medium heat just until hot; remove from heat. Add 1/2 cup mint leaves. Cover; let stand 30 minutes. Discard mint. Return cream to simmering over medium heat.
In small bowl, beat egg yolks with electric mixer on high speed about 3 minutes or until thick and lemon colored. Slowly beat in sugar. Gradually stir half of the hot cream into egg yolk mixture, then stir back into hot cream in saucepan. Cook over low heat about 5 minutes, stirring constantly, until mixture thickens (do not boil).
Stir in chocolate until melted. Transfer to medium bowl; refrigerate about 2 hours, stirring occasionally, until chilled.
In chilled large deep bowl, beat remaining 1 1/2 cups whipping cream with electric mixer on high speed until stiff peaks form. Fold chocolate mixture into whipped cream. Spoon mousse into dessert dishes. Refrigerate until serving. Garnish with mint sprigs. Store covered in refrigerator.