@brightlights:
That looks like a pretty good recipe. There is a lot of variation out there due to geography and families having their own recipes. Eggplant is integral though, and potatoes are usually present. I like to boil potato slices, then gently fry them in peanut oil until slightly crispy and use them as a base layer rather than a middle layer.
I feel that lamb is necessary to get the correct flavour profile. It works with the spices involved. Cinnamon, for example, complements lamb nicely, but it's hard to imagine it would enhance beef or turkey.
The bechamel sauce is what completes the dish. It should be thick, almost too thick to pour, and sprinkled with nutmeg.
Let me know how it turns out.