Final answer:
The common secondary sauces of Béchamel sauce are Mornay and Velouté.
Step-by-step explanation:
The common secondary sauces of Béchamel sauce are Mornay and Velouté. Béchamel sauce is a basic white sauce made from a roux (equal parts of flour and butter) and milk. Mornay sauce is a Béchamel sauce that is enriched with grated cheese, usually Gruyere or Parmesan. Velouté sauce is also a Béchamel sauce that is made with stock (commonly chicken or fish stock) instead of milk.