While there’s no rule saying you can’t use duck eggs in place of chicken eggs when baking, duck eggs have a different composition, and the results won’t be the same.
Duck eggs contain both more protein and fat than chicken eggs, which can have a tremendous impact on the texture and flavor of baked goods, but there are ways to mitigate this.
The standard ratio for a duck-to-chicken egg substitution is 2:3, which means two duck eggs are equivalent to three chicken eggs. However, you need to make some extra adjustments.
You’ll have to experiment with reducing the amounts of other fats and liquids in the recipe, such as using less butter or milk, to account for the protein and fat in duck eggs.
With proper care, duck eggs can yield naturally yellow and fluffy cakes, silky meringues, and creamy custards. You just have to figure out the changes that work for a recipe.