Add 1 cup dry hot cocoa mix and ½ cup cold heavy whipping cream to large mixing bowl. Using hand mixer (or stand mixer) with whisk attachment, mix ingredients together on low speed 15 to 20 seconds, then increase speed to medium. Continue mixing until cocoa mix and heavy cream are fully combined, then set mixer aside.
Add 1 7-ounce jar marshmallow creme to mixing bowl. Gently fold marshmallow creme into cocoa mixture using silicone spatula.
Once marshmallow creme is just incorporated, add 1 8-ounce tub Cool Whip. Gently fold in Cool Whip until just incorporated.
Once Cool Whip is just incorporated, add 1 cup mini marshmallows and ¼ cup mini chocolate chips to mixing bowl. Fold in marshmallows and chocolate chips until just incorporated.
If Serving Immediately: Transfer mixture to serving bowl and top hot cocoa dip with holiday sprinkles of choice, mini marshmallows, and mini chocolate chips if desired.
If Making in Advance: Transfer mixture to airtight container and refrigerate until ready to serve (no more than 24 hours). 30 minutes prior to serving, remove dip from refrigerator and set out at room temperature to soften. Transfer softened dip mixture to serving bowl then top with holiday sprinkles of choice, mini marshmallows, and mini chocolate chips if desired.
Serve immediately with Belgian butter waffle cookies, graham crackers, rolled wafers, fresh strawberries, and/or pretzel crisps.