01 - Add milk, ice cubes, vanilla ice cream, vanilla bean seeds or extract, and sugar to a blender.
02 - Blend on high speed until completely smooth and creamy, about 30-60 seconds.
03 - Taste the mixture and add more sugar if desired. Blend again briefly to incorporate.
04 - Pour into two tall glasses, top with whipped cream if using, and serve right away with straws.