Prepare the Chicken and Vegetables: In a large pan, heat some oil over medium heat.

Add the chopped leek and sauté until soft.

Add the diced chicken fillet to the pan and cook until browned. Add a bit of water if necessary to prevent sticking.

Add the sliced mushrooms and minced garlic. Cook until the mushrooms are soft and the chicken is fully cooked.

Stir in the diced tomato and tomato sauce. Season with salt, black pepper, and "Spring Green" spice mix. Cook for another 5 minutes, then set aside.

Prepare the Béchamel Sauce: In a separate saucepan, melt the butter over medium heat.

Add the flour and stir constantly to form a roux. Cook for about 1-2 minutes.

Gradually add the milk, stirring constantly to avoid lumps. Continue to cook until the sauce thickens.

Season with salt and nutmeg to taste.

Add 100g of the grated cheese to the sauce and stir until melted and well combined.

Assemble the Lasagna: Preheat your oven to 180°C (350°F).

In a large baking dish, spread a thin layer of the béchamel sauce on the bottom.

Place 3 lasagna sheets over the sauce.

Spread a layer of the chicken and mushroom mixture over the lasagna sheets.

Cover with another layer of béchamel sauce.

Repeat the layers (lasagna sheets, chicken mixture, béchamel sauce) until all the ingredients are used, finishing with a layer of béchamel sauce.

Sprinkle the remaining 100g of grated cheese on top.

Bake the Lasagna: Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes.

Remove the foil and bake for an additional 10 minutes, or until the cheese is golden and bubbly.

Serve: Let the lasagna cool for a few minutes before serving.

Enjoy your delicious Chicken and Mushroom Lasagna!