Chewy Bechamel while making Moussaka After making my moussaka from a recipe online I couldn't help but notice that the bechamel didn't bubble when it was in the oven and when it was done the bechamel became chewy. What could be the reason for this? 

Recipe for bechamel:
335ml milk (although I used this initially I found the bechamel to be VERY thick when making roux so I added a tea cup of milk while making the roux)

1 small onion

salt and pepper, to taste

35g butter

35g flour

50g mozzarella cheese, for topping
It may have been the mozzarella. When traditional Greek moussaka is topped with grated cheese, it is usually a harder, aged variety, such as Kefalotyri or Parmigiano-Reggiano. To thin the bechamel with additional milk, after the roux is complete, is fine. The roux should be very thick, as it's only flour and butter. It thins when the liquid is added, then thickens again as it simmers. However, if your bechamel was too thin and the cheese melted into it, that may account for the chewy result.