A gluttonous girl named Shirley has been reborn in another world, only to discover a devastating problem. This new world lacks hamburgers, beef bowls, ramen, and practically all the modern convenience foods she loved in her previous life. Refusing to accept this bland reality, she declares she will simply make them herself. Shirley dedicates herself to recreating modern dishes from scratch using the available ingredients in this fantasy world.

As Shirley busies herself cooking each day, rumors of her unique and delicious creations begin to spread through her town. Her expertise lies in B-grade gourmet food and sweets, which are utterly foreign to the people of this realm. Eventually, her culinary reputation reaches the royal palace. A scout arrives with an unexpected offer: to become a maid tasked specifically with making snacks for the prince.

Shirley accepts the position, partly because the palace offers better kitchen facilities than she has at home. Appointed as the head of a new fifth maid brigade, her primary responsibility is preparing treats for the young prince, referred to as the young master. The prince has been withdrawn and sad ever since losing his mother. However, Shirley's comforting and unfamiliar modern dishes gradually begin to break through his grief, restoring his smile and bringing warmth back to his life.

The story follows Shirley as she navigates royal palace life, introducing one modern dish after another. She uses her knowledge from her past life to create potato chips, flan, doughnuts, hot dogs, ramen, gyudon, and even chocolate, often improvising when specific ingredients do not exist in this world. Her creations cause a sensation, or go viral, within the palace as nobles and servants alike become captivated by her three-star cuisine. The narrative focuses on her culinary experiments, her relationships with the palace staff and the young prince, and the ripple effects of introducing modern comfort food into a fantasy royal court.