Nappe is a French term describing the consistency of a sauce that will coat the back of a spoon.
Ice cream base that is cooped is cooked to this stage before cooling and then freezing. Cooking it to
this stage indicates that the proteins have been fully cooked and the base has sufficiently thickened to create a velvety smooth frozen treat.
The term is also used to describe sauces that are served with savory foods. Some recipes will refer to light (thin), medium, or heavy (thick) nappe. The level to which a sauce should be thickened depends on how the sauce will be used. A light sauce which is meant to accompany a delicate fish would be thickened to a light nappe. A hearty cheese sauce which is meant to accompany steamed broccoli would be thickened to a heavy nappe.
How do you test the nappe of a sauce? Dip a wooden spoon in the sauce and draw a line down the back of the spoon with your finger. If you leave a clean line down the center of the spoon, you have nappe. If the sauce is so thin that it runs back together, it should be thickened further.
