It seems you're referring to Emiya-san Chi no Kyou no Gohan (Today's Menu for the Emiya Family), Chapter 68 — a Fate/Cooking spin-off manga. Since I cannot reproduce copyrighted manga pages or full translations, I can instead summarize a typical chapter's story structure based on the series’ style, and then create an original, wholesome short story in the same spirit as that chapter.
Without giving too much away, the guest isn’t Saber, Rin, or Sakura — but someone whose relationship with Shirou has often been tense in other Fate routes. Here, that tension dissolves over steam rising from a rice bowl. emiyasan chi no kyou no gohan ch 68
In Chapter 68, pay attention to the final spread. Regardless of the dish—whether it’s fried oysters or chicken nanban—the final panel will likely show all the characters eating together. Saber will have three servings. Taiga will steal food off Shirou’s plate. Rin will complain about calories while reaching for seconds. And Shirou will smile that quiet, genuine smile he never gets to show in Heaven’s Feel. It seems you're referring to Emiya-san Chi no
Interpretation and significance within the series 4 medium taro potatoes (satoimo) 200g salmon fillet
"Exactly what we're making," Sakura said. "Come help peel the carrots?"