It is a bit of an effort finding fresh hay and lavender that haven’t been treated with pesticides and are suitable for cooking, but if you can, this dish is a real crowd pleaser.
Preheat the oven to 180°C/350°F/gas mark 4. Smear the lamb with the softened butter and season. In a heavy cooking pot (preferably one with a lid) put a layer of all the fresh herbs, half the hay and all the lavender at the bottom. Add the garlic and bay leaves.