Prepare up to two days in advance.
Simmer the orange juice and the jam in a saucepan until the mixture is reduced by half. Stir in the liqueur and cool.
Thinly peel two oranges and reserve the peel for the garnish.
Peel the remaining oranges, removing as much pith as possible. Place the oranges in a bowl and pour the cooled sauce over them. Chill.
To prepare the garnish, cut the reserved peel into very thin strips. Bring 1 cup of the water to the boil, add the peel and simmer for 8 minutes. Drain and rinse in cold water.
Bring the remaining ¼ cup of water to the boil. Stir in the sugar, until dissolved. Add the peel and simmer for 5 minutes. Remove with a slotted spoon and drain on paper towels. Toss in the caster sugar. Reserve the syrup and add to the oranges when cool.
Top each orange with a little peel. Excellent served with créme fraiche.