1. Preheat your oven to 375°F (190°C).

2. In a large skillet cook the ground beef over medium-high heat until browned breaking it up into small pieces as it cooks. Drain excess fat.

3. Add the chopped onion and mushroom to the skillet and cook until the vegetables are softened.

4. In a separate saucepan melt 2 tablespoons (30g) of butter over medium heat. Whisk in 2 tablespoons (30g) of flour to make a roux cooking for 1-2 minutes.

5. Gradually whisk in 1 cup (250ml) of whole milk and cook stirring constantly until the sauce thickens.

6. Remove the sauce from heat and stir in 1 cup (115g) of grated cheese until melted and smooth. Season with salt and black pepper to taste.

7. In a large bowl beat 1 egg and set aside.

8. Arrange 4 lasagna sheets on the bottom of a 9x13-inch (23x33cm) baking dish. Spread half of the meat mixture over the pasta followed by half of the béchamel sauce.

9. Repeat the layers starting with the lasagna sheets the remaining meat mixture and the remaining béchamel sauce.

10. Top the lasagna with the beaten egg and sprinkle with 1/2 cup (55g) of grated cheese.

11. Cover the dish with aluminum foil and bake for 30 minutes.

12. Remove the foil and continue baking for an additional 10-15 minutes or until the top is golden brown.