- In a bowl, combine ¼ cup (55 g) of the butter with the flour. Set aside.
- In a pot over medium heat, soften the onion and garlic in the remaining butter. Add the celeriac, milk and broth. Bring to a boil. Cover and simmer for 20 minutes or until the celeriac is tender. Add the butter-flour mixture and whisk to combine. Cook for 2 minutes.
- In a blender, purée the béchamel until smooth. Keep warm.
- With the rack in the middle position, preheat the oven to 350°F (180°C).
- In a food processor, finely chop the carrots, celery and leek.
- In another pot over medium-high heat, cook the chicken in the butter, breaking it up with a wooden spoon, for 15 minutes or until lightly browned. Add the vegetables and cook for 5 minutes. Add the wine and spices. Simmer for 5 minutes. Add the béchamel sauce and Parmesan. Season with salt and pepper. Mix well.
- Meanwhile, in a large pot of salted boiling water, cook the lasagne noodles until al dente. Drain and lightly oil.
- In a 13 x 9-inch (33 x 23 cm) baking dish, spread out 2 cups (500 ml) of the chicken sauce. Sprinkle with 1/4 cup of mozzarella. Cover with a layer of noodles. Repeat with the remaining ingredients, finishing with the remaining sauce and mozzarella. Place on a baking sheet.
- Bake for 45 minutes or until the cheese starts to brown. Finish cooking under the broiler for 3 minutes, if desired. Let sit for 15 minutes before serving.
In order to get 4 layers of noodles, you will need between 12 and 15 lasagna noodles, depending on the brand you use and the size of your baking dish.