How to Make It
In a bowl, blend the Dijon mustard and mustard seeds. Season the rabbit parts with salt and pepper. Spread the mustard all over the rabbit pieces. Cover and refrigerate overnight.
Preheat the oven to 325°. In a large nonstick skillet, heat the oil. Add the rabbit pieces and cook over moderate heat until richly browned, about 2 minutes per side; turn the pieces carefully to keep as much mustard crust on the rabbit as possible. Transfer the rabbit to a plate.
Add the onion, fennel, thyme, rosemary and sage to the skillet. Cover and cook over moderate heat, stirring occasionally, until the vegetables are softened, about 10 minutes. Add the wine and cook, scraping up the browned bits from the bottom of the pan. Add the stock and bring to a boil. Nestle the rabbit pieces in the vegetables.
Cover the skillet and braise the rabbit in the upper third of the oven for about 50 minutes, until is tender. Uncover and braise for 10 minutes longer, until the rabbit pieces are glazed.
Transfer the rabbit to a plate. Discard the herbs. Boil the sauce over high heat until the liquid is reduced by two-thirds, about 5 minutes. Season with salt and pepper and return the rabbit pieces to the sauce to heat through. Serve in shallow bowls over polenta.