Heat a comal, cast-iron, or heavy bottomed pan to medium-high heat. Place the tomatillos, garlic, onion, and Serrano peppers directly on the hot pan. They will become soft and slightly blackened, about 7 – 10 min.
Flip tomatillos, peppers, onion, and garlic over and continue to char for 10 more minutes.
Remove ingredients from griddle and set aside.
Start grinding ingredients in molcajete one at a time. Once the desired consistency is reached, add the next ingredient and keep grinding. Season with salt and pepper and serve.
If you do not have a molcajete you can use a blender or food processor. Simply place all the cooked ingredients in the machine and pulse until the desired consistency is reached.
Season to taste.
If you do not have a molcajete you can use a blender or food processor.