Melt chocolates and butter in the microwave (1 minute on high and stir, then 1 more minute on high) or in a double boiler (stirring often). Add flour and sugar in chocolate mixture. NOTE: Mixture will become thick.
Stir in beaten eggs/egg yolks. Stir until smooth. Stir in the vanilla and orange liqueur. Divide batter evenly among custard cups.
Bake 14 minutes. Edges will be firm, but center will be runny. Run knife around edges to loosen and invert on plate.