Combine the marinade spices and moisten with wine vinegar.
Rub the spice mixture over the lamb.
Chill the lamb for 3 to 4 hours.
Heat oil in a roasting tin until very hot.
Add the lamb and unpeeled garlic head to the tin and baste with hot oil.
Roast in a preheated oven at 200°C for approximately 1.5 hours.
Baste the lamb frequently during roasting.
Remove the lamb and rest it while preparing the gravy.
Simmer the stock, garlic, chilli, cinnamon, and coriander seeds.
Place the roasting tin over a medium flame.
Deglaze the tin with Ricard and scrape the sediment.
Strain the spiced brown stock.
Add the stock to the roasting tin and simmer for 10 minutes.
Toast fennel seeds on a heavy griddle until darkened.
Strain the gravy into a saucepan and press the garlic for flavor.
Stir roasted fennel seeds into the gravy.
Whisk a mixture of butter and flour into the boiling gravy.
Simmer for 4 minutes and re-season before serving.