California Walnut and Mushroom Lasagna

For the filling

• 50 g butter unsalted
• 2 cloves garlic peeled and minced
• 300 g chestnut mushrooms minced
• 200 g portobello mushrooms sliced
• 300 g leaf spinach
• 200 g walnuts finely chopped
• 50 g plain flour
• 100 ml white wine
• 320 ml whole milk
• 100 ml double cream
• ½ tsp nutmeg grated
• 50 g cheddar grated
• 50 g parmesan cheese grated
• 100 g taleggio cut into chunks
• 50 g parsley finely chopped
• 1 tbsp Dijon mustard
• 1 lemon

To build

• 300 g lasagna sheets fresh, blanched
• 250 g ricotta
• 50 g cheddar grated
• 50 g parmesan cheese grated