In medium saucepan, stir together sweetened condensed milk and cocoa. Cook over low heat, stirring constantly, until mixture is smooth and slightly thickened, about 10 minutes. Remove from heat; cool slightly. Gradually add whipping cream, half-and-half and vanilla, beating with whisk until well-blended; refrigerate until cold. Place in ice cream freezer container and freeze according to manufacturer’s instructions.
Makes 1-1/2 quarts/litres (18 servings).