Koutei Heika to Odokumi Yaku no Isekai Manyuu Gourmet Tabi

The current Emperor of the Doom Empire, Peregrin I, and his poison taster, Marcus. On their way back from a secret trip to the castle town to enjoy some "common" delicacies that aren't available at court, the two are attacked by someone. They fight back, but are chased by patrols, and the two instinctively jump into another "portal"... You're sure to get hungry after reading this. A gourmet fantasy featuring a master-servant duo begins!! (Source: Shinshokan, translated)