Technically, the chocolate would be illegal... and here's why:
31 CFR § 515.204 Importation of and dealings in certain merchandise.
(a) Except as specifically authorized by the Secretary of the Treasury (or any person, agency, or instrumentality designated by him) by means of regulations, rulings, instructions, licenses, or otherwise, no person subject to the jurisdiction of the United States may purchase, transport, import, or otherwise deal in or engage in any transaction with respect to any merchandise outside the United States if such merchandise:
(1) Is of Cuban origin; or
(2) Is or has been located in or transported from or through Cuba; or
(3) Is made or derived in whole or in part of any article which is the growth, produce or manufacture of Cuba.
And just as important:
§ 515.410 Dealing abroad in Cuban origin commodities.
Section 515.204 prohibits, unless licensed, the importation of commodities of Cuban origin. It also prohibits, unless licensed, persons subject to the jurisdiction of the United States from purchasing, transporting or otherwise dealing in commodities of Cuban origin which are outside the United States.
Seeds may be a bit of a different story, I'd imagine, but I'm just speculating.
If I take Cuban seeds and grow them in Nica, it would seem that the plant that grew would be derived from an article of produce of Cuba, and the sale of the leaves (whether or not in the form of a cigar) is probably illegal in the US.
But that said... if I take those seeds, grow a plant in Nica, then harvest the seeds from that plant and replant them in Nica, is it still a Cuban seed? Seems to me that the seed es de Nica, but it's still a derivation from Cuba.
Food for thought...