Prep:

Cup of Yum
1. Start heating up the slow cooker, either on high or low heat, to get the bowl warm.
2. In a microwave-safe bowl, heat up 2 cups of milk for 2 minutes until it's hot, not boiling.
3. Pour the hot milk into the bowl of the slow cooker and add the chocolate chips. With a whisk, stir to start melting the chocolate chips with the hot milk. Pour the rest of the milk and half and half into the slow cooker and combine.

Cook:

1. Cook on low for for 2 to 3 hours or on high for 45 minutes to 1 hour. Add the vanilla at the very end and stir.
2. When it's time to serve it, reduce the heat to the warm setting. If your slow cooker doesn't have a warm setting, reduce it to low and stir occasionally to prevent burning at the bottom of the pot.

Serve:

1. Laddle out the hot chocolate into mugs and top with marshmallows and additional chocolate chips.