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Remove the seeds and the stems from the ancho chiles, then cover them with hot water. Allow them to sit for 15-20 minutes, until they're soft. Drain the peppers.
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Place the anchos, Tobasco, black pepper, cumin, oregano, garlic, onion and oil into a food processor and process into a smooth paste.
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Place the skirt steaks into a gallon sized zip-top bag and spoon the marinade onto the meat. Make sure to fully cover the meat, then refrigerate for at least 1 hour, or up to 24.