Preheat the oven to 180°C conventional oven/ 160°C fan-forced (350° Fahrenheit/Gas 4). Grease a baking dish with butter or margarine.
To make the pumpkin and sage sauce, melt butter in a medium-sized saucepan over medium heat. Add the chopped and whole sage leaves and cook until crisp. Remove the 12 whole sage leaves to serve and set aside. Add the red onion and garlic to the saucepan with butter and sage. Add the pumpkin, then pour over the vegetable stock and bring to the boil. Reduce the heat to low and gently simmer until the pumpkin is tender (approximately 15-20 minutes). Allow to cool slightly, then blend.
Tip: When blending the pumpkin and sage sauce, add the pieces of pumpkin, herbs and very little liquid to start with. Add more liquid to the blender, as required, to achieve the required sauce consistency.
To make the Besciamella sauce, melt the butter in a medium-sized saucepan over medium heat until foaming. Add the flour and stir with a wooden spoon to form a smooth paste (a roux). Allow the flour and butter mixture to cook for a minute (but do not allow it to brown). Remove from the heat. Slowly pour the cold milk into the roux, stirring constantly, until the mixture is smooth. Add the bay leaf and return to medium heat. Cook, stirring with the wooden spoon until the Besciamella comes to the boil and thickens (approximately 10 minutes). Remove from heat. Season with salt to taste and stir in freshly grated nutmeg. Set aside to cool slightly.
Remove the dried lasagne sheets from the packet.
Note: If you wish to make your own pasta for this recipe, use 1 quantity of fresh egg pasta. If you are using fresh egg pasta, divide the dough into 2 or 3 pieces. Use a pasta machine to roll out the dough, starting with the highest setting. Fold the pasta sheet in half, then roll out through the pasta machine several times to laminate the pasta. Adjust the setting on the pasta machine and fold the pasta sheet in half each time you feed the pasta dough into the machine until the dough is very thin (approximately 1-2mm).
Ladle pumpkin and sage sauce and besciamella sauce to just cover the base of the baking dish. Cover with a layer of pasta sheets that overlap slightly. Spoon pumpkin and sage sauce where the pasta overlaps. Ladle 1/3 of the pumpkin and sage sauce over the pasta sheets. Spread 1/3 of the besciamella sauce over the pumpkin and sage sauce. Spoon half of the ricotta cheese over the besciamella. Continue layering with the pasta sheets, pumpkin and sage sauce, besciamella sauce and ricotta. Finish with a layer of pasta, pumpkin and sage sauce, besciamella sauce and Parmigiano Reggiano sprinkled to cover the lasagne.
Bake in a preheated oven for 40 minutes. Remove from the oven. To confirm that the lasagne is cooked, insert a knife in the centre of the baking dish and hold it there for a few seconds – if the knife blade is hot, the lasagne is ready. Leave to rest for a minimum of 10 minutes before serving.
Cut the Pumpkin, sage and ricotta lasagne into 6 portions. Top with crispy sage and serve – buon appetito.