Preheat the oven to 190C/gas 5.
2. For the dukkah spice mix, warm the hazelnuts, chickpeas, coriander seeds and cumin seeds in a frying pan, over a gentle heat. This helps draw out, and intensify the flavours.
3. Transfer to a food processor, and add the peppercorns, salt and mint leaves. Process until it becomes a smooth powder.
4. For the can can birds, wrap each can in tin foil. This prevents any pigment from the can's covering tainting the meat. Stuff each bird with a bay leaf, cinnamon stick and red chilli. Divide the coriander and cumin seeds between each bird and add to the other spices. Turn the chicken upright, so the legs are pointing towards you. Insert the can inside the cavity of each bird - this might be quite a tight squeeze! Stand the cans on 2 roasting tins - the birds shouldn't touch the roasting tins and will be suspended on the cans.
5. Drizzle the chickens with olive oil and scatter with half the dukkah spice mixture.
6. Roast the chickens in the oven for around 1 hour before smearing with Dijon mustard. Sprinkle over the remaining dukkha spice blend.
Serve the chickens straight away with the sweet potato wedges and a leafy salad on the side.