I’m a pastry chef with a flock of ducks and I’ll second what therealtimshady said! Baking’s a bitch! Did you sub out the egg quantity directly or did you measure your ingredients on a scale? Breaking up your eggs and whisking them thoroughly, then measuring the weight may help avoid this fat/protein separation issue. Or it may not (please refer to previous statement about baking). An average chicken egg is said to be about 50 grams, so two would give you 100g. Our average duck egg weighs about 90 grams, so two would give you 180; a significant difference! But I will say I have never seen that happen before.