Combine sea salt, demerara sugar and ground cinnamon in a small bowl and set aside.
Bring duck breasts to room temperature for 30 minutes. Using a sharp knife, carefully cut away any excess skin/fat, leaving a 1/4 inch layer. Score the skin in a criss cross pattern, taking care not to cut all the way through the fat to the flesh.
Season the skin with salt and pepper.
Bring a pan to a medium-high heat and fry the duck, skin side down, for 5 minutes or so, until it begins to crisp up. If the pan starts to smoke turn the heat down.
Turn the duck over and sprinkle the skin side with the cinnamon sugar mixture. Cook for a further 2 minutes before turning the duck again, sprinkling the bottom with the remaining mixture. Cook for one minute longer and remove the duck from the pan.
Transfer the duck breasts to a baking tray with a wire rack in it and cook in the oven for 8-12 minutes for medium rare, 15-18 minutes for medium.
Saute the shallot in the duck fat remaining in the pan (remove any excess if there's too much fat).
Deglaze the pan with the port and add the chicken stock and fresh thyme. Simmer for 5 minutes until it reduces slightly.
Thicken with the cornflour dissolved in a little water and add the fresh raspberries. Take care not to allow the sauce to boil as you don't want the raspberries to dissolve.
Remove the pan from the heat, add the butter and stir.
Let the duck rest for 5 minutes before cutting into thick slices. Serve with the raspberry port sauce, some seasonal greens and rice.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.