We open the can of tomatillos and remove 6 of them to a freezer safe plastic bag for another use. We drain the rest of the can over the sink and pour into our food processor. We carefully split our rinsed serranos and remove the stems and most of the seeds. We add these to the processor. We peel and then coarsely chop our onion and garlic and add as well. We add the lettuce, cumin, cinnamon, and cloves, and freshly grate in some black pepper. We take a handful of cilantro from the fridge and wash it well. We add to the processor and puree until well mixed.
Our immersion blender came with a mini-chop attachment. We use this to grind the cooled-off toasted pepitas. When finely ground, we pour into a bowl. We microwave our homemade stock until hot and pour over the ground pepitas. We stir well.
To our pan, we add the oil and start heating over medium heat. When hot, we add the pepita-stock mixture and “fry”, stirring constantly for a few minutes. The mixture gets a darker color and thickens quickly. Next, we add the contents of the food processor, some salt, and continue to cook for a few more minutes.
We add the canned chicken stock (boxed actually), and stir well. We lower the heat to medium-low and simmer for 30 minutes, stirring occasionally. The sauce thickens and the flavors meld. We taste for salt.
We add the chicken when the sauce is a good consistency and heat through.