avoir le beurre et l'argent du beurre

to want two incompatible things at once

Said of anyone after two mutually exclusive good things at the same time, all the perks and none of the trade-offs. The fuller saying even throws in 'and the dairymaid's smile' for good measure.

Il veut télétravailler tous les jours et garder son bureau individuel : il veut le beurre et l'argent du beurre.

He wants to work from home every day and keep his private office: he wants it both ways.

First turns up in print in 1896, in an economic essay by Numa Droz, making the plain point that in any transaction you give something to get something. It draws on simple market logic: a farmer can sell the butter or keep it, never both.