Makes approximately 1½ cups
¼ cup cumin seeds
¼ cup coriander seeds
¼ cup fennel seeds
¼ cup yellow mustard seeds
2 pasilla chiles, stemmed, seeded, deveined, and torn into small pieces
2 ancho chiles, stemmed, seeded, deveined, and torn into small pieces
½ cup dried whole oregano (preferably Mexican)
2 tablespoons onion powder
2 tablespoons garlic powder
¼ cup Spanish paprika (pimento), preferably sweet or hot
Heat a dry skillet over medium-low heat. Pour in the cumin, coriander, fennel, and mustard seeds along with the pieces of pasilla and ancho chiles. Toast, stirring constantly, until it is very aromatic and just beings to smoke, about 3 minutes.
Dump the mixture onto a plate and let it cool to room temperature. Grind it to a fine powder in a spice grinder or clean coffee grinder.
Put the powder in a large bowl and add the oregano, onion powder, garlic powder, and paprika. Stir them really well to combine.
Store the adobo in an airtight container or resealable plastic bag in a cool, dark place for up to a month.