Episode 4 of "Bon Appétit, Your Majesty" kicks off with an exhilarating culinary clash between Ji-young, Chef Eom, and Chef Maeng. Dowager Queen In-ju grandly announces the theme of filial piety, with tofu and doenjang (soybean paste) serving as the pivotal ingredients. Ji-young makes a heartfelt decision to recreate the doenjang pasta her father once lovingly prepared for her.
As the competition ignites, Chef Eom and Chef Maeng hastily seize the majority of the ingredients, leaving Ji-young with mere crushed tofu and a scant amount of doenjang. In a stroke of luck, she also snatches some spinach, a vegetable recently introduced to the kingdom and unfamiliar to many.
Eunuch Yoon, ever the Unexpected Santa, offers Ji-young some doenjang—albeit not as exquisite as the others'—and shares a poignant tale. He recounts how Queen In-ju's mother, in her final meal before entering the palace, savored a doenjang soup with a uniquely refreshing savory taste that no chef has been able to replicate since.
Inspired by this revelation, Ji-young decides to forge ahead with the soup rather than the pasta. As she delves into her cooking, a lightbulb moment strikes—she knows precisely which ingredient will lend that elusive refreshing savoriness to her soup. Determined, she ventures out to procure it, only to be halted by the unyielding guards. Yi Heon, with a hint of malice, offers her a conditional pass: if she fails, she risks losing both her arms.
Time slips away, and realizing the urgency, Ji-young tasks Gil-geum with fetching the ingredient. Without hesitation, Gil-geum dashes off. En route back, she encounters Chu-wol, Consort Kang's handmaiden, who topples her to the ground. But Gil gum persists and ultimately returns, breathlessly handing Ji young a basket.
As Ji-young conjures her masterpiece, the royals eye the spinach with curiosity, unfamiliar with its incorporation in such a manner. Soon, the buzzer sounds, signaling the end of the competition. Each chef presents their creation.
Chef Maeng wows the crowd with dumplings wrapped in fish, the doenjang limited to a dipping sauce—a minor disappointment for Yi Heon. Next, Chef Eom presents Tofu Yeonpotang, a delightful fusion of pan-fried tofu and soup. Finally, it's Ji-young's turn.
To the royals' astonishment, they are served a humble bowl of doenjang soup. Their first sip, however, leaves them utterly amazed. Dowager Queen In-ju is transported back in time, reminiscing about her mother's final meal, tears welling up in her eyes. The secret ingredient? Clams, unveiled with a flourish.
When Ji-young explains the health benefits of spinach, Queen In-ju is delighted, her palate enchanted by both flavors and sentiment.
Ji-young is proclaimed the victorious champion! Nonetheless, Yi Heon remains steadfast in his vow and commands his henchmen to amputate the arms of the rival chefs. Intervening swiftly, Ji-young implores Yi Heon, elucidating that to a chef, the loss of an arm is akin to a death sentence. Even Queen In-ju joins in, confessing that the competition was merely a vehicle to humiliate Ji-young. As compassionate pleas for clemency resonate through the crowd, Yi Heon feels a sudden wave of dizziness but manages to steady himself. Conceding, he grants reprieve to the chefs, urging them to emulate Ji-young's excellence.
Later, in a hushed conspiracy, Queen In-ju and the other consorts deliberate on whether Yi Heon is privy to the tragic fate of his mother—deposed and poisoned, their whispers reveal.
Returning to the heart of the kitchen, Ji-young is greeted with heartfelt gratitude from her fellow chefs, whose lives she has spared. Gil-geum confides that she was incapacitated by an unknown assailant but was rescued by Gong-gil, allowing her to make a triumphant return to the competition. Their humble abode is then visited by Song-jae, who subtly hints to Ji-young that her survival was not solely predicated on her culinary prowess. Yi Heon, he suggests, played a silent role in her triumph, though he refrains from elaborating further.
Yielding to his suspicions, Yi Heon storms into Consort Kang's chambers, accusing her of targeting Ji-young. She counters by reminding him of his diverted focus from the quest to uncover his mother's murderer. The conversation is abruptly interrupted as the king is overcome by another bout of dizziness, compelling him to retreat unsteadily to his quarters.
Elsewhere, Prince Jesan discovers to his astonishment that Director Kim Yang-son preemptively took matters into his own hands, defying Jesan's express instructions to wait. Without authorization, he hired an assassin to target Yi Heon. Through his informant, Jesan learns that this assassin was a nimble, masked figure—a subtle clue pointing unmistakably towards Gong-gil!
Upon Ji-young's arrival in the kitchen, Eunuch Yoon hastily informs her that the king is enduring one of his perilous fits. She comprehends that these episodes are treacherous moments where Yi Heon lashes out violently towards everyone within his reach. With compassion in her heart, Ji-young prepares doenjang pasta, believing it might bring him solace. When they present him with the meal, he orders everyone except Ji-young to exit his presence. Despite his turbulent emotions, the king finds solace in the pasta's taste. Ji-young reminisces that her father would prepare this dish for her whenever she felt distressed.
As their conversation delves into her father, Ji-young repeats her claim of being from the future, emphasizing her desperate need for the book in her bag to return. He implores her to reveal his future to him, but she hesitates, mindful of the dark events known as the Gapshin Literati Purge that lie ahead. During this purge, Yi Heon would exact revenge on those responsible for his mother's demise, only to face a rebellion that would ultimately depose him.
Subsequently, Yi Heon immortalizes Ji-young's dish in his writings, remembering her referring to her book as Mangunrok and adopting the same title for his diary. Later, we glimpse Ji-young's bag tucked away in a cupboard, yet the ownership of these quarters remains ambiguous. Just as Yi Heon inscribes his diary, the original Mangunrok mysteriously vanishes.
In a subsequent turn of events, Yi Heon receives devastating news: Yi Jang-yun, a draftsman entrusted with uncovering truths about his mother's demise, has been assassinated. Agitated by this setback, Yi Heon indulges in alcohol. Chang-seon rouses Ji-young from her rest and tasks her with preparing more food for Yi Heon. But as she offers him the meal, a drunken Yi Heon draws her nearer, his lips pressing against hers in an unexpected kiss.
