Prepare the pastry cream:

1. Mix together the egg yolks and sugar, then add the cornstarch and cocoa.

2. Heat the milk to a boil. Pour it over the previous mixture and whisk vigorously. Return this mixture to the saucepan and bring to a boil again. Let it cool completely.

3. Using a pastry bag with a tip, fill the éclairs with cold cream by making two small holes underneath.

4. Remove the zest from an orange. In a small saucepan, heat equal parts water and sugar, then plunge the orange zest into it and simmer over low heat until it becomes transparent (about 15 minutes).

5. Melt the icing in a double boiler and dip the top of the éclairs into it.

7. Finally, decorate with candied zest.