Season the shanks well with salt and pepper. Grind the fennel and coriander seeds coarsely in a spice grinder or clean coffee grinder and combine in a large baking dish with the flour, curry powder and chile powder. Add the shanks and dredge well in the mixture.
Heat a heavy Dutch oven just large enough to accommodate the shanks over high heat, add 2 tablespoon of the oil, and swirl to coat. When the oil shimmers, add the shanks in batches and brown on all sides, 8 minutes. Remove the shanks, wipe out the Dutch oven, and add the remaining 1 tablespoon of oil. When hot, add the onions, celery, carrots, ginger, and garlic and sauté, stirring, until the vegetables are soft, 6 to 8 minutes. Season with salt and pepper, add the wine, turn down the heat, and simmer to reduce it by half, 6 to 8 minutes.
Add the soy sauce, bananas, chiles and thyme. Return the shanks to the pot, add water to cover, and correct the seasonings; the liquid should have good saltiness. Cover and braise until the meat falls from the bones, 3 to 4 hours. Remove the shanks and reduce the liquid over medium heat until thickened slightly, about 10 minutes. Remove the thyme springs, if used, and with a hand or standard blender, puree the sauce. Correct the seasonings add the shanks to the sauce and keep warm.
Serve Braised Curried Lamb Shanks with couscous, rice, polenta or even pasta.