On Milkshakes and Mysteries

Making milkshakes is a mystery to me. I mean, sure I can put the milk in the blender and plop in the ice cream and then hit the button, but. . . I never get it quite right. There must be instructions somewhere, some secret that other people know that I missed. By the time I finally get the proportions of milk to ice cream adjusted, I've got enough to serve me and all four cats (which would please them just fine), but that's not what I wanted. I just wanted a simple, one serving milkshake.

What's the secret?

I obviously had my nose in a book when the Milkshake Mystery was explained to mankind.