For the organic orange sugar syrup, wash hot, rub dry and finely grate the peel. Bring 200 ml water, sugar and orange peel to the boil and simmer for about 6 minutes. Let it cool down.
Wash the remaining oranges and rub dry. Cut all oranges in half, squeeze carefully so that the halves do not break. Using a spoon, scrape the rest of the flesh and partitions completely out of the orange halves (except the organic orange). Freeze the orange peel.
Mix sugar syrup and orange juice. Pour into a bowl and allow to freeze for approx. 1 hour, stirring vigorously with a whisk every 20 minutes.
Beat the egg white until stiff and fold into the frozen mixture. Freeze for another 4 hours, stirring well every 30 minutes. Use an ice-cream scoop to make scoops out of the sorbet mixture and freeze again for about 1 hour.
Arrange orange sorbet in the frozen orange peel and serve immediately.