Place minced peppers, 1/4 cup of the chopped cilantro, and the diced onions on a cutting board. Chop them together into very small pieces. Sprinkle with kosher salt. Using the flat side of the knife blade, smear the mixture to work it into a paste, and chop again to achieve as fine a texture as possible.
Stem, halve, and pit the avocados. Scoop out flesh and place in a bowl. Add 1/4 cup chopped cilantro, onion and serrano mixture, salt, and fresh lime juice. Mash with a potato masher to desired texture (smooth or chunky), 5 or 6 minutes. Taste and adjust seasonings. If not serving immediately, cover and refrigerate.