1. Bring your loin of lamb out of your fridge and allow it to rest at room temperature whilst you make your stuffing.
2. In a small frying pan, gently warm your coriander and cumin seeds. Grab a medium to large bowl and pour in your spices.
3. In the same pan drizzle in your olive oil. Gently fry your onions until soft and golden brown. Add these to your bowl, along with the rest of your ingredients, barring your loin of lamb. Mix together thoroughly.
4. Lay your loin of lamb on a large board. If it is already rolled and tied, carefully cut your butchers string and unroll the layer of fat from around your joint until the point the muscle just about remains attached. Spoon in your stuffing mix and pat down to ensure it is firm.
5. Gently roll your joint back up, capturing the stuffing, before tying back up with string.
6. Sear in your pan for 2-3 minutes on all sides to seal, before transfering to a 180C oven for a further 20 minutes.
7. Remove from your oven and cover loosely, and rest for 15 minutes before serving - just enough time to pour yourself a glass of wine!