Preheat oven to 400 degrees Farenheit. You will bake on center rack.
Take a 9 X 13 inch baking pan and grease it with 1 1/2 tablespoons of olive oil.
Sprinkle about 1/2 tablespoon of mizithra on bottom of pan
Layer half the pasta on the bottom of the pan. Toss with 2 1/2 tablespoons of mizithra until evenly coated.
Using a slotted spoon, spread the meat mixture over the pasta. The slotted spoon is important as your meat sauce might have a fair amount of liquid and you want to drain most of this off. You can use as much of the meat as you would like but be sure that there is a fine layer of meat covering all of the pasta, as shown above.
Sprinkle about 1/4 teaspoon nutmeg on top of the meat.
Spread the rest of the pasta on top of the meat mixture and then top this layer of pasta with 1/4 cup grated mizithra cheese.
Pour the prepared béchamel sauce over the pasta. Use the back of a spoon to spread it evenly, ensuring that all of the noodles are covered with sauce.
Then, take a fork and insert it in several areas over the pastitsio and wiggle it around. This will help the béchamel seep in between the top layer of the noodles.
Sprinkle the 1 teaspoon of mizithra on top of the béchamel.
Bake pastitsio on the center rack of oven, uncovered, for approximately 50 minutes. Keep an eye on your pastitsio. You may want to turn your pan halfway through the cooking process if it is browning unevenly. You may also want to set your oven to broil for the last minute of baking in order to brown it more significantly on top
Let sit for 20-30 minutes before cutting and serving.