Shrimp and Green Lasagna

16 green lasagna sheets
4 Tbsp butter
1 large onion, finely chopped
1 leek, chopped
2 celery stalks, finely chopped
125 ml (½ cup) plain (all-purpose) flour
60 ml (¼ cup) dry white wine
500 ml (2 cups) warm vegetable broth
750 ml (3 cups) light cream (12%)
1 tsp grated nutmeg
450 g (1 lb) cooked small shrimp, chopped
Salt and pepper
100 g (3 oz) Parmesan cheese, grated

1.In a large saucepan filled with salted boiling water, cook green lasagna sheets al dente. Drain and transfer to a clean humid towel.
2.Preheat oven to 190°C (375°F).
3.In a saucepan, melt butter. Cook onion, leek and celery for 5 minutes over low heat while stirring. Incorporate flour. Slowly whisk in white wine. Immediately add in vegetable broth. Add cream, whisking until sauce is thick and smooth. Whisk in nutmeg and chopped shrimp. Season lightly with salt and pepper. Remove sauce from heat and set aside.
4.In a large oven dish, place successive layers of green lasagna sheets, shrimp sauce and grated parmesan, finishing with grated Parmesan. Cover with aluminum foil. Transfer to oven and bake 30 minutes.
5.Remove foil and return to oven to bake 15 minutes. Remove from oven and let cool 5 minutes before serving.