When you prepare delicate food: use au bain marie cooking. Also for food that can easily overcook or disintegrate, we recommend au bain marie cooking. This technique uses a water bath as heat source for the pan. Thus, dosage of the heat takes place in a careful manner and the heated surface never exceeds 100 C. I prefer to use a pan with a thin bottom. So that when you remove the pan away from the steam, no further heat addition takes place. Also continuous stirring when making sauces prevents exceeding the recommended temperature.
For example, when making warm egg sauces such as a sabayonne or hollandaise and bearnaise sauces, the temperature should not exceed around 75 C. When you make it warmer, egg proteins will completely coagulate and the sauces start to separate. You will have to learn from practice when the sauces become more viscous and bind and when the sauces went too hot and separate.
Another application of au bain marie cooking we find when we bake a terrine or pate in the oven. The terrine is placed in a pan filled with water in the oven. This causes the outside of the terrine not to exceed 100 C and prevents the pate from over and uneven cooking.