Add the oil to a large pot on medium high heat along with the chopped onion and minced garlic. Stir for 1 minute until aromatic and onion begins looking translucent.
Add the beef and lamb mince and mix using a wooden spoon until mince is broken up and brown.
Next, add the remaining ingredients and stir to combine. Cover with a lid and cook for 45 minutes on low heat until thickened. Take the bay leaves and cinnamon stick out using tongs. Set aside to cool completely.
Greek Béchamel Sauce
Add the butter to a large saucepan and melt. Add the flour and mix using a spoon or spatula until well combined.
Next, add half the milk and mix until smooth. Then add the remaining milk and mix.
Slowly pour in the beaten egg as you mix until it’s all been added. Then add the cheese and nutmeg and stir until well combined and the cheese is mostly melted. It may look slightly lumpy after adding the cheese, that’s normal.
Pasta
Cook the pasta according to your packet instructions. Subtract 2 minutes from the cooking time to make assembling easier. Drain well and add back into the pot. Add about 1 1/2 cups of bechamel sauce and use tongs or pasta stirrer to mix and coat the pasta in the sauce.
Assembly
Preheat your oven to 180C / 350F. To get a nice looking slice of pastitsio lay the pasta in a deep rectangle baking dish ( roughly around 9.6cm in height and 40.5cm in width) all in one direction. I used tongs to do this. It can be tedious but is worth it once you slice into it.
Next, top it with the cooled meat sauce and use a spoon or spatula to spread out evenly.
Lastly, pour the bechamel sauce over it and spread around before topping with more kefalotyri cheese. Bake for 30 minutes or until cheese on top goes golden.