For the Bechamel
1. Melt the butter in a saucepan over medium-low heat, stir in the flour.
2. Whisk in a little of the milk at a time, stirring continuously until you have a smooth, slightly thick sauce.
For the layering
Butter a large gratin or baking dish, and evenly lay a layer of lasagne sheets on top of this.
Scatter 1/4th of the pumpkin and the Gruyere cheese over the top and smear with dollops of 1/4th of the bechamel sauce, top with 1/4th of the basil leaves and sprinkle 1/4th of the ground nutmeg.
Repeat the above until you have used all the ingredients, cover with foil and bake in a preheated oven at 350 degrees Fahrenheit for 30 minutes
Increase oven heat to 400 degrees Fahrenheit, remove the foil and allow the top to colour for another 10 minutes