I consider myself a bit of an expert bc I eat a lot of chiles. However I have the same problem you guys state. I buy serranos to eat, they are all the same hot. Jalapeños are still the best base for salsa etc, but bc they are unpredictable we keep serranos or habaneros and add to mixture if it's not hot enough with jalapeños.
My guess is it's how and where they are grown, we're probably getting some from New York City. 😉
CH3NO2
Bookmarks