Clean the tomatillos by removing the husk. Use running water to wash the tomatillos and the serrano peppers. Peel the garlic cloves. Cut a small bunch of cilantro and clean with running water. Let it rest on a towel to dry.
In a skillet roast the green pepitas slightly, make sure not to burn. The pumpkin seeds are roasted to release some of the oils for a tasty nutty flavor.
In a comal or a skillet roast the tomatillos, the serranos, and the garlic. Make sure to toast well as this roasting process is what gives the authentic Mexican flavor.
Place all ingredients in the blender, add some water, granulated sea salt, and cumin.
Blend until getting a thick sauce and store on a mason jar or a plastic container with a lid. Keep refrigerated or freeze.
The secret to obtaining the authentic flavors is to toast the ingredients before blending.
The pepitas should not be toasted too much to maintain their characteristic green color.