The unilateral promise is the contract by which one party, the promisor, grants to the other, the beneficiary, the right to opt for the conclusion of a contract whose essential elements are determined, and for the formation of which only the consent of the beneficiary is lacking.
Revocation of the promise during the time allowed to the beneficiary to opt does not prevent the formation of the promised contract.
A contract concluded in breach of the unilateral promise with a third party who knew of its existence is void.