The strudel scene in Quentin Tarantino’s 2009 film “Inglorious Basterds” is often mistaken as Landa's tactic to determine whether Shosanna is Jewish. However, Shoshanna would eat the non-kosher strudel willingly even if she was an Orthodox Jew, because dietary laws are “suspended when the situation requires you [to] do it to protect your life,” according to the “Inglorious Basterds” Fandom page.

The point of the strudel scene is to build suspense, because by ordering a glass of milk for Shosanna and insisting that she add cream to her strudel, Landa’s skills as a self-proclaimed “Jew Hunter” are brought to the audience's attention. Of course, the first time the two met was on the dairy farm where he murdered Shosanna’s family.

Even if he wanted to, it would've been impossible for Landa to use a strudel to test if Shosanna was Jewish. However, his presence alone was enough to kick the tension into high gear during an otherwise casual conversation over strudel.