Why 1 egg use to 125 ml of milk in an custard?

There's no strict rule that says you *must* use 1 egg for 125 ml of milk in custard. The ratio of eggs to milk in custard is more of a guideline, and can vary depending on the desired consistency and richness of the custard.

Here's why:

* Desired Texture: A higher proportion of eggs to milk will result in a thicker, richer custard. A lower proportion will make a thinner, lighter custard.

* Personal Preference: Some people prefer their custard with a strong egg flavor, while others prefer a milder taste.

* Type of Custard: Different types of custard (like crème anglaise vs. pastry cream) often have different ratios of eggs and milk.

* Cooking Method: The amount of liquid evaporation during cooking can affect the final consistency.

General Guidelines:

* Standard Ratio: A common starting point for a classic custard is 1 egg yolk per 125 ml of milk, which will make a smooth, creamy custard.

* Thicker Custard: For a thicker custard, you can increase the egg yolks to 2 per 125 ml of milk.

* Lighter Custard: If you want a lighter custard, you can use 1 egg yolk per 150-200 ml of milk.

Remember: The best way to find the perfect ratio for you is to experiment and adjust it to your liking!