Have all your ingredients measured and ready. Now we make the sauce. Please follow these steps and you will get a nice smooth sauce! First melt the butter in a pan, then add the flour.
Use a wooden spoon and stir very well, until it is all combined like the photo. Keep stirring this mix for 1 minute on a medium heat. You need to cook the starch. Then remove from the heat.
Start by adding 3 Tablespoons of the milk. Combine using the spoon, stirring until it is combined. Then add ⅓ of the milk, again, stir until it is combined.
Keep stirring the mixture, it will take a couple of minutes, and you will get lumps like in the photo. Don't worry at this stage! The lumps will go, so long as you stir. Use your wooden spoon to make sure none of the flour is stuck in the sides of the pan. At this stage, return the pan to a medium heat, and add the remaining milk.
If you have a hand whisk, switch to using it now, and add the mustard, salt and herbs. Continue to stir until the sauce becomes thick and holds to the whisk. It should be a 'coating' consistency. Be patient, it will seem like nothing is happening for a while, then suddenly, hey presto! The sauce immediately thickens. Keep stirring!
When it has thickened, add the grated cheese and stir in well. The sauce is now ready for serving or using in a casserole. Please enjoy!
