Toast and soak the chiles. Bring a small saucepan of water to a boil then remove from heat. Heat a comal or dry cast iron skillet over medium-low heat. Add chiles to the comal and toast, turning frequently, until fragrant and starting to change color (about 4 minutes). Submerge chiles in the hot water and let soak until very tender, about 15 minutes. 

Blend spice mixture. Drain chiles and place in the blender with remaining ingredients, except pork. Blend on high until smooth. You may have to stop and scrape down the blender to get everything blended evenly. 

Combine with pork. Mix ground pork with spice mixture in a large bowl. Use you hands to mix evenly and make sure all the pork is coated with the spice mixture. 

To cook chorizo. To cook the chorizo, heat a tablespoon of vegetable oil in a large skillet over medium-high heat. Add chorizo and cook, stirring frequently, until sausage is cooked through and the color has changed from bright red to reddish-brown, about 5-8 minutes.

To store the chorizo. If not cooking right away, store chorizo in a tightly-sealed container in the refrigerator for up to 3 days or place in freezer-safe plastic bags, seal tightly, and freeze for up to 6 months.