Step 1 Heat 2 tablespoons of the olive oil in a large, deep skillet over medium-high heat. Dust the lamb shank with the flour (reserve any remaining flour) and brown on all sides, about 7 minutes. Remove the lamb from the skillet, reduce the heat to medium and add the remaining tablespoon of oil. Add the onion and cook until tender and lightly browned, about 5 minutes. Add the garlic, brown sugar, vinegar, bay leaf and thyme. Stir to dissolve the sugar. Add any remaining flour.
Step 2 Gradually add the broth and beer to the mixture and bring to a boil. Scrape up any browned bits. Reduce the heat to low and return the lamb to the skillet. Cover and cook over low heat until the meat is tender, about 2 hours. Season to taste with salt and pepper. Remove the bay leaf.