Love your recipe and the how simple you made it sound , Moussaka is really time consuming, but at the end its all worth. I make mine vegetarian , instead of Mince i use puy lentils and mushrooms , with loads of spices like cumin , coriander , pinch of cayenne , smoked paprika and spring onions, depends on the occasion sometimes i experiment even by adding gram masala ( Indian type of mix spices) not traditional at all but works very well, the thickness of the filling comes from slowly cooked tin tomatoes till they become like thick paste , then add spoon full of tomato paste and mix with the lentil and mushrooms. Give it a try!