Place beans into a pressure cooker and fill with enough water to cover the beans by 1 inch. Bring to a boil, and boil for 2 minutes. Remove from the heat, drain and cool for 1 hour.
Add water to the beans again, filling just enough to cover the beans by 1/2 inch. Season with salt, fennel seed, cayenne pepper and mixed peppercorns. Put the lid on and set the pressure to high, or 15 pounds depending on your indicator. Bring to a boil and cook for 35 minutes. Let the pressure lower naturally before releasing the lid, according to manufacturer's instructions (about 15 minutes). Serve hot.