Add the whole milk and sweetened condensed milk to a 4-quart or larger slow cooker and whisk until combined.

Incorporate the semi-sweet chocolate chips and the maraschino cherry juice into the liquid mixture.

Cover the slow cooker and cook on the Low setting for 2 hours.

Whisk the mixture every 30 minutes during the cooking process to ensure the chocolate melts evenly and does not scorch on the bottom.

Once the chocolate is fully melted and incorporated, stir in the vanilla extract.

Adjust the slow cooker to the Warm setting for serving.

Ladle the hot chocolate into mugs and garnish with whipped cream and a maraschino cherry.