In a small pot melt the butter with the flour and grate nutmeg on top.
Cook the butter with the flour over medium heat por a minute, stirring the whole time with a whisk.
Remove the pot from the heat and add the milk little by little, stirring in between with the whisk. Once you've added all the milk return the pot to the heat.
Cook the bechamel sauce over medium heat whisking constantly so it doesn't burn nor form lumps. Once it starts to boil keep ir cooking for one extra minute and then turn off the heat.
Add salt and pepper to taste.
Spread a thin layer of bechamel sauce on the base of the mould. Place your first pasta sheets on top
After the pasta you add bolognese sauce, then bechamel and the grated cheese mix. You need to make this layer 3 times in total, always dividing with pasta.
The very last step is to place pasta sheets on top, spread a thin layer of bolognese and sprinkle parmesan cheese only. Parmesan goes nice and crispy in the oven.
Cook in a preheated oven at 180°C o 350°F for 30-45min or until you see it bubbling and golden on top.
Let the lasagne rest for at least 10 minutes before cutting into it. In this way you let all the liquids firm up a bit so it doesn't fall apart when you cut into it.