[UnpossibleJim]

Once you eat the cake, you can no longer possess it

EDIT:

Let me make it more clear, as English may not be your first language, if you're asking this question in truth (I sometimes miss sarcasm online, sorry).

Cakes can be beautiful things which people (of a certain time period, especially) wanted to show off as a sign of their wealth, as refined sugar was expensive. Once it was eaten, you could no longer display such wasteful extravagance.

[diogenesjunior]

i hate how americans always assume we are from there and understand everything they say

[mannerheim]

There's a similar idiom in a couple different languages. The French supposedly say 'avoir le beurre et l’argent du beurre' (have the butter and the money from [selling] the butter), and I once recalled hearing that there was a Spanish idiom along the lines of having a chicken in both the pot and in the yard, but alas I'm not able to find that phrase.

[UnpossibleJim]

| i hate how americans always assume we are from there and understand everything they say |

It's a forum where everyone was typing in English, so my first assumption was that English was your fist language. I didn't say anything about American. And I tried to fix my mistake =/

[diogenesjunior]

Oh, I wasn't talking about you. You were helpful.

[willcipriano]

Ey up duck, ever since I was cut and carried to me British trouble and strife, I've had to learn lots of slang it's done my lump of lead in.

[s1artibartfast]

It is actually an idiom originating in England in the 1500's.