This is much easier than the title would suggest and a wonderful way to use winter squash. I always buy a few in the fall to roast and puree, then I have them in convenient 2c blocks in my freezer for whenever I feel like a pie a souffle. You might be able to use a 15oz can of pumpkin for this, but I've never tried it. This is very popular with both my husband and daughter. If you want a light dinner for a small family, serve this with a salad, for a larger group it is a tasty and unexpected vegetable side dish.
1 1/2c half and half OR 12oz evaporated milk
2c cooked and pureed squash
6 eggs, separated
In a saucepan, whisk butter and flour constantly over medium heat. Gradually whisk in half and half or evaporated milk. When thick and bubbly, remove from heat and whisk into squash, egg yolks and salt.
Beat egg whites until stiff peaks form. Fold into squash mixture. (Or if you have a kitchen aid with a whisk beater, beat whites in kitchen aid, and then beat in the squash just until everything is mixed)
Pour batter into a buttered 2qt souffle dish or casserole.
Bake at 350 for 1hr and serve promptly. The top will be golden brown and nicely puffed.