eating cake

Of course, you can have your cake and eat it too, as long as you do it in that order. Similarly, you can halve your cake and eat it too. And what Marie Antoinette apparently had in mind, assuming she ever said anything of the kind, was brioche.

Less confusingly, but not sounding nearly as appetizing: Man kan ikke både blæse, og have mel i munden (you can't both blow and have flour in your mouth). Though, for the life of me, I can't figure out why you'd want to.