Duck or Chicken Eggs for Custard? Compare Edible Weight Before Substituting

One large duck egg is not necessarily the same amount of ingredient as one chicken egg. In custard, that difference changes the balance between egg and milk. Weigh beaten egg and keep pan size, sugar and cooking conditions consistent before deciding whether a substitution works for the dessert you want. Source 1

The regional tradition

Duck and chicken eggs can differ in size and in yolk-to-white proportion, so a one-for-one egg count may change a custard’s structure. Weighing beaten whole egg gives a more useful starting point. This simple whole-egg custard is a comparison method rather than a yolk-only leche flan formula; its texture will not match every flan recipe.

Ingredients and equipment

For each egg type, use 100 g beaten whole egg without shell, 200 ml pasteurised milk, 30 g sugar and optional ¼ tsp vanilla. Make one chicken-egg batch and one duck-egg batch, giving four small custards in total. Use four identical 180–200 ml ramekins, a roasting pan, sieve and thermometer. Preheat the conventional oven to 150°C, or 130°C fan.

Preparation, step by step

1. Crack sound eggs into separate bowls, wash hands and weigh 100 g beaten chicken egg and 100 g beaten duck egg. Keep any unused raw egg refrigerated.
2. For each bowl, dissolve 30 g sugar in 200 ml milk and combine gently with the egg and optional vanilla. Avoid whipping in a foam.
3. Strain and divide each mixture between two identical ramekins. Label the egg type on the tray so samples cannot be confused.
4. Place ramekins in a roasting pan and pour hot water around them to about halfway up their sides. Keep water out of the custard.
5. Bake for about 30–45 minutes, checking from 30 minutes. Each centre should be softly set and reach at least 71°C; remove individual cups as they finish.
6. Lift out carefully, cool promptly and refrigerate within two hours, or one hour above 32°C. Compare the samples at the same chilled serving temperature.
7. Assess smoothness, firmness and flavour without assuming every difference comes from species. Egg freshness, yolk proportion and uneven oven heat can also matter.

Texture and troubleshooting

A smooth custard has a softly set centre without liquid raw egg. Bubbles often come from vigorous mixing or excessive heat. A firmer duck-egg sample does not prove all duck eggs behave identically: their yolk proportion and size vary, so repeat the measured method when switching suppliers.

Buying and serving value

Compare egg prices per gram of edible contents rather than per shell. Also account for the milk and any mixture left in the bowl. A weighed substitution is easier to repeat, but an established commercial or yolk-only flan formula still needs its own ratio.

• Duck eggs larger than chicken eggs: Weigh edible contents rather than count shells. Size changes liquid-to-protein balance.
• Custard has bubbles: Mix gently and use controlled heat. Whisking and heat can distort comparisons.
• One sample remains unset: Continue safe cooking before serving. Taste tests do not excuse raw egg centres.

Weigh the edible egg before changing a custard recipe. Matching the rest of the method makes the comparison more useful.