When I was first introduced to kastera (Hangul: 카스테라), I was told that it was the Korean version of the Japanese kasutera, which is a sponge cake that the people of Nagasaki learned how to make from the Portuguese in the 16th century. Kasutera (Japanese: カステラ) is rectangular in shape and denser than what Americans know as sponge cake.
But after actively seeking out different variants of castella in Koreatown bakeries, I’ve come to the conclusion that Koreans use “kastera” to describe almost every type of baked product that’s Western in origin. An exaggeration, but I threw my hands up when I saw the label “dry” castella at Village Bakery (a place I like a lot by the way). Some look like cupcakes, most are oblong shaped, even square.
I have spotted genuine-looking Japanese kasutera (rectangular and firm, not so spongy) being sold at bakeries such as Paris Baguette, Bosco Cake Salon and Caketown Garden at prices slightly higher than the dubious-looking kastera.
Now I have to make clear that just because most variants of Korean castella don’t look like traditional Japanese kastera doesn’t mean they don’t taste better. In fact, I would say that Americans won’t take a liking to Japanese castella at all because the sweetness is too subtle. To try it, head to HK Super and buy Keifuudou, which is imported directly from Japan.
You just can’t say you like or don’t like Korean kastera in general, because each bakeshop has its own definition of what it is. Caketown Garden has corn kastera that like cornbread-flavored sponge cake. Paris Baguette has oblong-shaped kastera at $2 (see pic) and also more expensive, Japanese-looking rectangular kastera labeled “Mini Bon Delicieux.”
My personal adventure is going to all these different Korean bakeshops and trying to see what new incarnation of kastera / castella / kasutera the Korean bakers come up with — mocha, green tea, herb, walnut, cheese… My problem though is that I eat them before I remember to take a picture for documentation. 
