Gather all ingredients. Preheat the oven to 300 degrees F (150 degrees C).
Heat olive oil in a skillet over medium-high heat. Season lamb chops with salt and pepper. Sear lamb in hot oil until browned, 1 to 2 minutes per side. Remove chops to a plate, reserving drippings in the skillet.
Sauté onion and garlic in reserved drippings over medium heat until onion is tender, about 5 minutes. Remove from heat.
Transfer lamb chops to a baking dish; add onion mixture. Sprinkle rosemary over chops. Pour beef broth and red wine into the baking dish. Cover the dish with aluminum foil.
Bake in the preheated oven for 3 hours. Remove lamb chops to a serving platter.
Carefully pour liquid from the baking dish into a saucepan. Whisk together water and cornstarch in a bowl until no lumps remain; stir into liquid in the saucepan. Add Worcestershire sauce and cook over medium heat until thickened, about 5 minutes.