Gratin of pumpkin or squash

Place the squash/pumpkin and 4 tablespoons of water in a saucepan, cover and cook for 20 mins till tender. Remove the lid and boil to evaporate the water, set aside to cool. Preheat the over to 180c.
Beat the egg yokes and sugar together. Slightly mash the squash and add to the egg along with two thirds of the cheese. Season to taste with salt and pepper.
Whisk the egg whites in a seperate bowl till soft peaks form, whisk in the lemon juice. Carefully fold into the puree mixture, tast and adjust seasoning.
Butter a 24x30cm gratin dish. Pour in the mixture, sprinkle over the remaining cheese and dot with the butter. Bake for 15 to 20 minutes.