Heat half-and-half in 2-quart saucepan over medium heat just until hot. Gradually stir at least half of the hot half-and-half into egg yolk mixture; stir back into hot half-and-half in saucepan. Cook over low heat about 5 minutes, stirring constantly, until mixture thickens (do not boil). Stir in chocolate chips until melted. Cover and refrigerate about 2 hours, stirring occasionally, just until chilled.