Preheat the oven to 160ºC.
Mash the rosemary, mint, garlic and anchovies together. Spread half of this mixture over the inside of the meat, tie the meat with string, and rub the rest over the lamb.
Place in a roasting tray with the lemons and drizzle with olive oil. Roast for 1½ hours. Squeeze the lemon juice over the lamb, remove and cover with muslin.
Add Verjuice to pan juices. Over medium heat, stir to deglaze pan. Pour gravy over meat.
For the Béarnaise sauce: Place the onion, vinegar, peppercorns and tarragon or thyme in a small saucepan. Bring to the boil and cook until about 2 tbsp of liquid remains. Cool and strain.
Pour into a bowl and beat in egg yolks. Place the bowl over a pan of simmering water. Whisk until the mixture has thickened a little and starts to turn pale and creamy. Add the butter a little at a time and whisk it in until the sauce has thickened. Season.
To serve: Serve lamb with the Béarnaise sauce.
Recipe reprinted with permission of Lose It!
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