To cook the flour
Heat the butter in a pan. Cook the flour in the warm butter over a medium heat, stirring with a whisk. The flour must not take on any colour. Remove the pan from the heat.
Add the milk and cream to the flour in one go, bring to the boil while stirring, reduce the heat. Season the sauce, simmer over a medium heat for approx. 10 mins., stirring occasionally until the sauce is thick and creamy.
Béchamel sauce can easily be turned into a cheese sauce. Simply mix the cheese into the Béchamel sauce, season.