Preheat oven to 220C (425F)
Whip yolks, sugar, vanilla, and Grand Mariner. Whip whites until firm but moist. Fold yolk into whites. Turn oven down to 180C (350F). Pour mixture into buttered and sugared soufflé cups or ramekins.
Bake 13 minutes. Serve by slitting top in cross and add warm rich chocolate sauce.
I used small ramekins 3 inch or 7.5 cm in diameter.