Heat anchos in stock in a pot over a low simmer to reconstitute them. Purée into a sauce in a food processor and reserve.
Heat EVOO, a turn of the pan, in a pot over medium-high heat, add meat and crumble into fine bits as it browns. Add onions and garlic, and cook to soften a few minutes more. Season with salt, pepper, cumin, coriander and paprika.
Stir together the brown sugar, vinegar, Worcestershire and tomato sauce for the sloppy sauce. Pour sloppy sauce and ancho sauce into a pot and stir to combine. Bring to a simmer to thicken and combine flavors, 5 minutes. Serve with soft slider rolls and toppers.