In a medium pot, melt butter over medium heat. When the butter has completely melted, add the flour and whisk until smooth, about 2 minutes. Gradually add the milk, whisking constantly to prevent any lumps from forming. Add salt, nutmeg, and pepper and continue to simmer and whisk over medium heat until the sauce is thick, smooth and creamy, about 5 - 8 minutes. The sauce should be thick enough to coat the back of a wooden spoon. Remove from heat and check for seasoning. Set aside.
Preheat oven to 375º F. Line a large baking sheet with aluminum foil.
Spray with butter a 13 x 9-inch baking dish. Spread 1/2 cup of the bechamel sauce into the bottom.
Arrange the 3 pasta sheets side by side, covering the bottom of the baking dish. Evenly spread a layer of bolognese sauce, about 2 cups. Spread 1 1/2 cup of the bechamel sauce. Sprinkle 1/2 cup of parmesan cheese on top. Arrange another 3 layers of the pasta sheet, bolognese sauce, bechamel sauce, and parmesan cheese. Repeat. Arrange the final layer of pasta sheets and top with remaining béchamel, Parmesan cheese and mozzarella cheese.
Cover the lasagna dish with aluminum foil and place it on the baking sheet. Bake on the middle rack of the oven for 45 - 50 minutes, or until top is bubbling and the pasta is tender. Remove cover and continue to bake for about 15 minutes or until the cheese on top becomes golden.
Let it rest for 8- 10 minutes before serving.
STORING: Store in an airtight container in the fridge for up to 3 days. Reheat the lasagna in the oven or microwave until heated through.FREEZER: To freeze before baking, baking it, cover the tray tightly with a layer of plastic wrap, then the entire tray with aluminum foil, and freeze the whole pan for up to 3 months. When ready to enjoy, thaw and bake as instructed. To freeze after baking, let the lasagna cool to room temperature and the store like the above or cut into individual portions before freezing.QUICK TIPS:
Some people like to add ham to the pasticho, if you are one of them, you can add the ham slices over the bolognese sauce layer.
When you let the lasagna rest before serving, it will keep the lasagna from becoming runny and help it to keep its shape when cut.
Feel free to swap the meat in the bolognese sauce to whatever you have on hand. Try ground turkey or pork!
If you are a vegetable fan, feel free to sneak some in there! Grated carrots, diced mushrooms, or bell peppers make for an excellent addition to the pasticho.
Add some red pepper flakes or cayenne peppers to the sauce to give your lasagna some extra heat.
Be sure to grease your casserole dish so your lasagna can come out easily.