Finely mince the onion and jalapeno, removing the seeds from the jalapeno for a cleaner heat. Chop the cilantro and set aside. In your molcajete, add the minced onion, minced jalapeno, and about half of the cilantro along with the kosher salt and freshly squeezed lime juice. Using the stone pestle, grind these ingredients together with circular motions until they form a fragrant paste—this process releases the oils and flavors, creating a flavorful base that will season the entire guacamole. I like to take my time with this step because grinding rather than just stirring creates a much more textured, authentic result.

While the base is developing, cut each avocado in half lengthwise, remove the pit, and scoop the flesh into the molcajete. Work gently to preserve some texture—you want a rustic guacamole with visible chunks of avocado, not a smooth paste. I find it's best to add the avocados in batches rather than all at once, which gives you better control over the final texture.

Gently fold the avocado into the aromatics mixture using your pestle and a light hand—fold rather than grind to maintain a chunky texture. Add the remaining cilantro and the ground cumin, folding them in carefully. Taste and adjust seasoning with additional salt or lime juice as needed, remembering that the flavors will continue to develop slightly. Serve immediately in the molcajete for an authentic presentation.