Heat water in a large Dutch oven
Remove the outer wrap of the tomatillo and rinse. I've added additional tomatillos anticipating a couple will be unusable
Add tomatillos and jalapenos to the water and boil until tender, about 15 minutes. Remove and set aside to cool.
Add the onions, garlic, cilantro, and tomatillos to the blender
Cut off the top stem of the jalapeno, cut it into 3 pieces, and add to the blender
Pulsate the blender until the contents are smooth but still maintaining some texture
Heat the olive oil over medium heat. When hot, add the puree and stir for about five minutes. You want it to darken and thicken.
Add the chicken stock and stir to combine. Bring to boil and simmer until it becomes a thicker consistency. This may take 10 to 20 minutes. You do not want the sauce to be watery.
Add the salt and stir into the sauce.
Test it with a crispy corn tortilla. The flavor will develop more as it cools.