WTH is the author thinking with this world. For a world based on medieval Europe, it isn't medieval at all.
• They don't have sandwiches.
They had sandwiches, of course! Putting things in or on top of bread is literally an ancient idea! They didn't eat them as much because they had less things to put on the sandwich; both chocolate and peanuts come from the New World, and leaf vegetables weren't yet cultivated and pest-guarded enough to safely eat them raw. If you only have a little meat, you'd also want to eat the bone, hence you'd make a broth instead.
• Eggs are expensive.
Chicken were widespread, so eggs are much cheaper than actual meat.
• They don't know deep-frying.
Deep-frying only became mainstream across Europe when the potato was introduced from the New World, e.g. as fish&chips in the UK. But large parts of Europe were already familiar with deep-frying fish, and a Roman cookbook describes deep-fried chicken in a white sauce. Of course that idea didn't disappear with the fall of the Roman Empire. (And the Ottomans liked fried cheese.) The Japanese literally learned tempura from late-medieval Portuguese.
• They don't have noodles.
Pasta originates from the Eastern Mediterranean, but indeed didn't really spread to and within Europe. They had the ingredients and cultural contact, so presumably pasta simply was too much or too heavy work. It only started to spread when pasta-making machines were introduced. I guess rhe chef might not know the amount of effort involved and might therefore be interested, but he would give up quickly.
/rant, but very tired of authors who don't know anything about medieval Europe and assume their modern (often Japanese) cuisine would spread quickly. It wouldn't; the limit has always been work, ingredients and pesticide, not creativity.
EDIT: Next chapter has potato's and she uses bamboo. She might have created the latter, but bloody potato's‽ And they have no frying culture‽‽