Step 1

Place a large saucepan on a low heat and add the butter.

Step 2

Once melted, add the flour and use a whisk to mix together into a thick paste. Continue to cook for around 30 seconds to one minute, stirring constantly.

Step 3

Pour in approximately 100ml of the milk and continue stirring until it forms a smooth, thick paste with no lumps.

Step 4

Continue to add the milk, around 100ml at a time, stirring constantly. Each time, only add the next lot of milk when all the lumps are gone. Once all the milk has been added, you should have a smooth, thick white sauce.

Step 5

Continue to stir until it starts to bubble, simmer for 30 seconds, then turn off the heat. Generously season with salt and pepper and stir well.