01 -
In a microwave-safe bowl, heat 1 cup of heavy cream on high for 1 minute. Whisk in the cocoa powder until fully dissolved and smooth.
02 -
Transfer the cocoa mixture to a 4-quart crockpot insert. Add remaining 2 1/2 cups heavy cream, whole milk, sweetened condensed milk, and vanilla extract. Whisk until thoroughly combined.
03 -
Incorporate the semi-sweet chocolate chips into the mixture and stir evenly.
04 -
Cover with lid and set crockpot to LOW. Heat for 2-3 hours, whisking every 20-30 minutes to prevent burning and promote even melting of chocolate chips.
05 -
Once smooth and fully heated, whisk well, switch crockpot to WARM for up to 2 hours. Serve by ladling into mugs and garnish with mini marshmallows if desired.