Gochugaru is the soul of Korean cooking. It’s a coarsely ground Korean chili powder with a specific flavor profile: slightly sweet, smoky, and moderately spicy. You can’t just throw cayenne pepper into your tteokbokki and expect it to work. If you’re out, your best bet is a mix of Aleppo pepper and a tiny pinch of smoked paprika to mimic the mild heat and fruity smokiness.