Heat your oven to 220°C/Fan 200°C/Gas 7. Cut the fennel in half, from top to bottom. Peel off the tough outer layer. If the bulb is young and tender, you can leave this layer on. Lay the halves flat and cut out the root, leaving enough to keep the fennel intact, then cut each half into 4 wedges lengthways.
Place the 8 fennel pieces in a roasting tin. Add 180ml water, a pinch of salt and 2 tbsp olive oil. Slice half the lemon, bruise the garlic clove and add both. Cover the tray tightly with foil and bake for 15 mins. Remove from the oven and turn the fennel pieces over, cover with foil and cook for a further 15 mins, or till they're tender and cooked through. Once the fennel is cooked turn the oven down to 120°C/Fan 100°C/Gas 1/2.
Meanwhile, drain the haricot beans and rinse under cold running water for a few mins. Pick 6 sage leaves from the stalks.
Fold the beans through the hot fennel, cover again with foil and leave in the oven to keep warm.
Heat a heavy-based frying pan over a high heat. Rub 2 tbsp oil over the lamb leg steaks with 1/4 tsp salt and some pepper. Place into the hot frying pan. Don’t overcrowd the pan, cooking one by one if
necessary. Leave the steaks to cook for 2 mins,
without moving. Turn the steaks over, top with
the butter and sage leaves and cook for a further
2 mins for medium-rare, basting the steak and sage
in butter till crisp. Remove the pan from the heat,
squeeze over a little lemon juice and allow the
meat to rest for a minimum of 4 mins.
Spoon the braised fennel and haricot beans onto plates and top with the warm lamb leg steaks, crisp buttery sage leaves and a good spoonful of the resting juices.
Leftover sage leaves are moreish fried in butter until crisp and scattered over pasta or spiced pumpkin soup.