Chunyan Koushu no Bishoku Gaikouroku

The Kunlun Kingdom has been defeated by the Western powers and is now facing destruction. Reigetsu, the "unlucky" twin sister of the emperor, happens to meet Friedhelm, the archduke of the enemy Proja Empire. Brought in for her culinary skills, Reigetsu will play the role of the legendary chef "Chunyang" to engage in some dinner-table diplomacy, with the fate of her country at stake. She is pitted against the envoys of Western powers, the Empress Dowager still holding power over the puppet emperor, and various shadowy conspirators...... Can Reigetsu save her country with the help of the handsome but picky Archduke Friedhelm? Gastronomical diplomacy by the kitchen-girl princess is about to begin!

(Source: Hifumi Bunko, translated)