Remove approx. 50 ml of the orange juice (pure fruit juice without added sugar) and mix with the pudding powder and sugar.
Bring the remaining juice to a boil in a small, tall saucepan. When the juice boils, take it off the hob, stir in the mixed pudding powder and sugar and put it back on the stove. Bring to the boil at a low temperature while stirring. Keep stirring until the mixture thickens. Remove from the hotplate and let cool down.
Whilst it cools down, beat it through vigorously with the whisk from time to time.
In the meantime, peel the orange and remove the fillets from the skin and cut into small pieces.
When the mass has cooled down, pour the coffee milk into a mixing bowl and whisk until frothy with the electric hand mixer. Then pour into the orange mixture and stir again briefly and vigorously.
Stir in the orange pieces and then divide between four glasses or dessert bowls and let them set in the refrigerator.