Stir fry the spices (garlic, peppercorns, cumin seeds, etc), add chilies and stir, last, add tomatoes and onions.
Place all ingredients in a blender and blend until you’ll have a silky smooth sauce.
Add sauce to chicken, coat and marinate from 8 to 24 hrs.
Dip tortillas on birria oil, heat on a skillet, add some cheese and shredded chicken. Fold & Enjoy!