Mornay Sauce

Mornay sauce is a rich, creamy and cheesy sauce that is created by simply adding cheese (usually Gruyere and Parmesan) to Béchamel sauce. It can be used with a variety of dishes especially in gratins, with fish or as a base for cheese soufflés. The flavour profile for Mornay sauce can be adapted by varying the amount and the type of cheese used.

Things to look for when making Mornay sauce

Avoiding lumps

There are two things that can cause lumps in Mornay sauce. First, it’s a lumpy Béchamel sauce. To avoid this, follow the instructions described in the Béchamel sauce recipe. A quick fix for a lumpy Béchamel sauce is to pass it through a fine sieve; but if the correct process is followed, this should not be needed.
The second reason for a lumpy Mornay sauce is adding the cheese to the Béchamel too quickly or cheese that has not been grated finely enough. When this happens, the cheese will not melt easily in the sauce but instead clump together into big lumps. This is usually easy to fix, by heating the sauce gently (making sure it does not boil) and continue whisking until the lumps start to dissolve.

Ensuring the sauce does not split

When adding the cheese to the Béchamel sauce, you want the sauce to be hot enough so that the cheese melts but not too hot that the sauce starts to split. Usually, if the sauce gets to a boil, the cheese will start to split, making the sauce look and taste unpleasant.
To avoid this, turn off the heat before adding the cheese; the residual heat from the Béchamel sauce and the saucepan should be enough. Add the cheese in small gradual amounts and stir until it melts. If you see that the cheese is cooling down the sauce too much, put the saucepan back on a very low heat until all the cheese is incorporated into the sauce. Turn off the heat immediately after.

Avoiding a ‘stringy’ sauce

A good Mornay sauce should be smooth and creamy but not too cheese that it forms ‘strings’ when picked up with a spoon. The best way to avoid this is to use good quality aged cheeses like Gruyere and Parmesan. When young cheeses are used, you’ll tend to use more cheese relative to the amount of Béchamel because the flavour of the cheese is not strong enough. This leads the sauce consistency to become too cheese-heavy, which leads to a stringy sauce.

Storing Mornay sauce

Just like Béchamel sauce, Mornay sauce can be stored in the fridge for a few days. Ideally Mornay sauce should not be frozen as it may curdle when reheated. When heating up Mornay sauce, heat it up gently on very low heat or in a bain-marie.