1- Mix 2 C Milk, sugar, salt and chocolate chips in microwave bowl. Microwave on high for 5-7 Minutes. 2- Whisk this mixture until chocolate is incorporated well. 3- Mix remaining C of milk(cold) and cornstarch, and stir it into hot chocolate mixture. 4- Microwave for 3 more minutes, or until mixture thickens. 5- Stir in vanilla and serve.