To Uncurdle cheese sauce immediately halt the cooking process.
Take the pan off the heat and place it in an ice bath.
Also it's recommended adding an ice cube or two to your sauce to ensure it cools on the double.
If the clumps are relatively few, you can pour the whole sauce through a sieve.
Add a splash of the sauce's base liquid if it's a milk-based sauce, for example, pour in a few teaspoons of cold milk.
You may also add a splash of wine, beer or cream.
Whisk the sauce vigorously for about 10 seconds; this may be enough to repair a cheese sauce that's just beginning to curdle.
To fix grainy cheese sauce, remove it from the heat and let it cool.
Add a tablespoon of lemon juice to detangle the protein molecules and whisk to achieve a creamy smooth texture.
If you don't have lemon juice, you can use high-fat cream instead.
Curdling is especially common for cream or butter sauces.
Solution: If you spot it in time, then an ice bath is the quick-fix solution.
Remove the curdled sauce from heat immediately and place pan in an ice bath, which will immediately halt the cooking process.
How to make cheese sauce smooth.
Warm milk is slowly incorporated into the roux, creating a smooth mixture.
If you add the milk too quickly, use cold milk or simply don't whisk fast enough, you could get lumps in your sauce as bits of roux will cook and turn into small balls before they've had a chance to be smoothly blended into the milk.
Adding cheese to a bubbling mixture will cause the cheese to break down.
The emulsifiers and coagulants break down when heated thus causing a gritty texture.
Remove the hot béchamel from the heat.