Remove the skin from the duck breasts and reserve to make the crackling. Bring the water, pink salt, table salt and sugar up to the boil. Leave to cool and pour over the duck breasts making sure they are fully submerged in the liquid. Leave in the brine for 24 hours.
Remove the duck breasts from the brine and soak in cold water for 10 minutes. Place the breasts in a sous vide bag and co