Add the butter to a medium pot on medium heat and bring it to a boil.
Once the butter starts to boil, add in the flour, salt and pepper and whisk for 1 minute.
Slowly pour the milk in while whisking the whole time.
Once all the milk is added and it begins to boil, remove it from the heat.
Season to taste with additional salt and pepper if needed.
Garnish with dried parsley if wanted for a touch of colour.
Notes
The original recipe called for 1 teaspoon of salt which I found too salty for my liking, 3/4 teaspoon instead was perfect for me.It thickens more as it cools, and goes quite thick after being stored in the fridge.Store in the fridge for up to 2-3 days and re-heat gently on the stove.