Meanwhile, make the stuffing by mixing together the breadcrumbs, orange zest and juice, olives, thyme, a little salt and the olive oil.
Using baking parchment, line a roasting dish just large enough to hold the fennel halves snugly. Once they are cool enough to handle, take one half at a time and hold it in the palm of your hand, cut side up. Gently pull the layers apart, being careful not to break them off, and poke the stuffing in between them. Stuff all the fennel in the same way.
Lay them in the roasting dish, stuffed side facing up, and sprinkle any remaining stuffing over, then drizzle with the oil. Add the 4 tablespoons of hot water to the dish and bake in the centre of the oven until dark golden in colour and heated through.
Mix the watercress with the mint and place on 4 plates. Sit 2 stuffed fennel halves on top of each and scatter with any crumbs and juices from the roasting dish. Place a lemon wedge on the plate.
© 2007 Peter Gordon. All rights reserved.