How to Make It
In a heatproof bowl, cover the chiles with boiling water and let stand until softened, 20 minutes. Drain the chiles, reserving 1/2 cup of the soaking liquid. In a blender, puree the chiles with the reserved soaking liquid until smooth. Strain the puree through a fine sieve.
In a medium saucepan, heat the olive oil. Add the onion, garlic and a pinch of salt and cook over moderately high heat, stirring occasionally, until the onion is softened, about 4 minutes. Add the cumin, cinnamon, cloves, allspice and oregano and cook, stirring, until fragrant, about 1 minute. Stir in the chile puree, sesame seeds, breadcrumbs, chocolate and sugar and bring to a boil. Stir in the tomatoes, chicken stock, jam and vinegar and bring just to a simmer. Season the sauce with salt and keep warm.
Light a grill or preheat a grill pan. Brush the lamb with canola oil and season generously with salt and pepper. Grill over high heat, turning once, until lightly charred, about 5 minutes. Reduce the heat to moderate and grill until an instant-read thermometer inserted in the thickest part of the meat registers 135° for medium-rare or 140° for medium, about 20 minutes total. Transfer the lamb to a carving board and let rest for 10 minutes. Carve across the grain and serve with the warm ancho-huckleberry sauce.