Heyyy, Sakuya.Yes.I have.Ohhhh?Sakuya!You've eaten underwearrr.Yes.I have.You pervert!Have you ever made bread? / Have you ever eaten underpants?
Flandre is doing some wordplay which can be interpreted as either "pan tsukutta koto aru" ("have you ever made bread") or "pantsu kutta koto aru" ("have you ever eaten underpants"). Sakuya hears it as the former.
