Don't you just hate the skin that forms on your favorite sauce, custard or gravy? You make it beautifully, turn your back for five minutes and there it is, thick and congealed and almost impossible to remove completely.
Pros stop it forming by using a cartouche, which is simply a circle of baking parchment or grease-proof paper placed directly on top of the sauce or gravy.
To make one, start with a square of paper larger than the saucepan you have the sauce in. Fold two opposite corners together; you now have a triangle with one side longer than the other two. Fold this longer side in half and you have something resembling a coffee filter cone. Rest the broad end of the cone on the rim of the saucepan, so that the point is exactly in the centre of the pan itself. This tells you where to tear the cartouche.
Now tear off the broad bit of the triangle, following as near as possible the contour of the saucepan rim. Open out what remains and you will have a circle of paper which fits neatly inside the saucepan and rests on top of the sauce. Discard it before serving. No skin will ever form while it is in place.
