Use a 4-quart slow cooker. Add the milk and half-and-half to the insert, and then stir in the chocolate chips, and sugar. Add a dash of salt. If making flavored hot chocolate, add the peanut butter, or spices, or mint now also.
Stir everything together until the peanut butter has somewhat broken up a little
Cover and cook on Low for 4 hours or on High for about 2 hours. Stir at the half-way point to combine everything and allow to cook completely, until smooth.
Stir well again at finish and lade into mugs. Top with whipped cream, if you like and additional mini chocolate chips.
If you'd like a smoother texture, you can strain the finished hot chocolate through cheesecloth or a fine mesh strainer.
Make ahead: This hot chocolate is fabulous if made in advanced and then placed in refrigerator until needed for serving. Simply heat back up and serve.