Add white chocolate chips, condensed milk, 1 cup of the cream and the milk to a slow cooker
Cover and heat on low for about 2 hours
In a large bowl, add remaining 1 cup of cream, powdered sugar and vanilla
Using a hand mixer or stand mixer, whip until stiff peaks form
Serve mugs of hot chocolate with about a tablespoon of raspberry liqueur or to taste and a dollop of whipped cream as desired