Stout-Braised Short Ribs

Put oven rack in lower third of oven and preheat oven to 375 °F. Stir together brown sugar, paprika, curry powder, cumin, pepper, salt, and mustard in a small bowl until combined. Pat ribs dry and arrange in 1 layer in a shallow baking pan or a shallow dish, then generously coat all sides of ribs with spice mixture. Marinate, uncovered and chilled, 1 hour. Wash leeks in a bowl of cold water, agitating water, then lift out leeks and drain in a colander. Heat oil in pot over high heat until hot but not smoking and quickly brown ribs on all 3 meaty sides (but not bone side) without crowding, in batches if necessary, about 1 minute per side. Transfer meat to a large plate, then add leeks, carrots, celery, and bay leaves to pot and cook over moderately low heat, stirring occasionally, until vegetables begin to soften, about 3 minutes. Add garlic and cook, stirring, 1 minute. Add broth, beer, and tomatoes with their juice, then add ribs with any juices and remaining spices accumulated on plate and bring liquid to a boil, uncovered. Cover pot and transfer to oven, then braise until meat is very tender, 2 to 2 1/2 hours. Skim off excess fat from surface of sauce. Discard bay leaves.