To make the bechamel, melt the butter then whisk in the flour to create a roux. Cook for 30 seconds then slowly start whisking in the milk. You might not need all the milk, rather use too little and thin it out a little later.
Add the bay leaf, pepper and nutmeg then allow to simmer gently.
When the sauce has thickened and all the flour is cooked through, it's ready. Remove from the heat and set aside.
Layer the lasagna sheets with the bechamel, the shredded pork and provolone cheese. Repeat until all the ingredients have been used.
Top the lasagna with the grated Parmesan cheese and the sage leaves.
Place in the oven and allow to bake for 30-45 minutes until the pasta is cooked through and the lasagna is golden brown and crisp on top.
Remove from the oven and allow to rest for 10 minutes before serving.