Avoid a "floury" white sauce

At the beginning of a white sauce always cook off the butter and flour over low heat for 1 minute to ensure the finished sauce doesn’t have a “floury” flavour. Remove from the heat before whisking in milk and returning back to the heat to thicken. 

Reheating Hollandaise or Béarnaise sauce?

Never microwave! These are fragile emulsions and will split. Reheat by gently whisking over a double boiler on low heat. If the emulsion begins to split, try whisking in a spoonful of warm water, never add more butter.