To make orange custard, stir milk, cream, sugar, cardamom pods and zest in a saucepan over low heat until sugar is dissolved and mixture is hot.
Whisk egg yolks and flour until smooth and combined. Gradually whisk in hot milk mixture in a thin steady stream.
Return mixture to saucepan and cook, stirring, over low heat until thick. Pass through a sieve and into a bowl. Stir in Cointreau. Cover surface with plastic wrap and refrigerate until cold.
To make profiteroles, bring water and butter to a boil in a small saucepan. Remove from heat. Add flour and salt. Beat with a wooden spoon, until mixture leaves side of pan and forms a smooth ball. Remove from heat and cool slightly. Gradually beat in eggs, one at a time, beating well after each addition, until mixture is thick and glossy.
Spoon mixture into a piping bag fitted with a round nozzle. Pipe walnut-size balls, 4cm apart, onto prepared trays (will make about 20).
Bake 10 minutes or until puffed and golden. Reduce oven to 150C. Bake for a further 10 minutes or until crisp. Turn oven off. Cut a slit in base of profiteroles, to allow steam to escape. Return to oven for 10 minutes or until dry. Cool.
To make chocolate sauce, stir cream, sugar and zest in a saucepan over low heat until sugar dissolves and mixture is hot. Pour over chocolate in a bowl. Stir until smooth and melted. Stir in Cointreau.
Spoon or pipe custard into profiteroles. Drizzle with sauce.