Step 1

In a large, sturdy resealable plastic bag, combine the flour and chile powder with 1 tablespoon each of salt and pepper. Add the pork shanks, one at a time, and shake to coat thoroughly.

Step 2

In a large skillet, heat 2 tablespoons of the olive oil until shimmering. Add 3 of the pork shanks and cook over moderately high heat until browned all over, about 10 minutes. Transfer the browned shanks to a deep, heavy casserole. Wipe out the skillet and brown the remaining 3 pork shanks in the remaining 2 tablespoons of olive oil; lower the heat if necessary. Add the pork shanks to the casserole.

Step 3

Add the onion, carrots, celery and garlic to the skillet and cook over moderate heat until softened, about 5 minutes. Add the wine and bring to a boil. Simmer until slightly reduced, about 2 minutes. Pour the wine and vegetables over the pork. Add the stock, rosemary, bay leaves and thyme, season with salt and pepper and bring to a boil. Tuck the pork shanks into the liquid so that they're mostly submerged. Cover and cook over moderately low heat for 2 1/2 hours, or until the meat is very tender. Turn the pork shanks every 30 minutes to keep them submerged in the liquid. Transfer the braised shanks to a large, deep platter, cover and keep warm.

Step 4

Strain the liquid, pressing hard on the solids; discard the solids. Return the liquid to the casserole and boil until reduced to 4 cups, about 20 minutes. Spoon off the fat, pour the pork gravy over the braised shanks and serve.