Grilled Flank Steak with Prune-and-Pasilla Adobo - chiles

Method

• In a shallow, heatproof bowl, cover the pasillas with 1 cup boiling water; carefully top with a small plate to keep the pasillas submerged.
• Let the chiles stand until softened, about 20 minutes.
• Meanwhile, in a small saucepan, cover the prunes with water and bring to a boil.
• Cover and let stand until softened, about 10 minutes.
• Drain the prunes and transfer to a blender.
• Transfer the pasillas to a work surface; reserve 1/2 cup of the soaking liquid.
• Discard the pasilla stems and seeds and coarsely chop the chiles.
• Add the pasillas and their reserved soaking liquid to the blender and puree.
• Light a grill or preheat a grill pan.
• In a medium saucepan, heat the vegetable oil.
• Add the onion and garlic and cook over moderately low heat until softened, about 7 minutes.
• Add the pasilla chile-prune puree along with the sugar, cinnamon and sherry vinegar and bring to a simmer over moderately high heat.
• Stir in the mezcal and stock and simmer for 1 minute.
• Season the adobo sauce with salt and pepper.
• Season the flank steak with salt and pepper and coat it with 1/4 cup of the adobo sauce.
• Grill the steak over moderately high heat, turning once, until medium-rare, about 5 minutes per side.
• Transfer the steak to a carving board and let rest for 5 minutes.
• Thinly slice the steak across the grain and serve with the remaining pasilla-prune adobo sauce.