How to Make It
Preheat the oven to 350°. In separate saucepans, steam the squash and potato, until tender, 10 to 12 minutes. Press the potato through a fine sieve or a ricer. Puree the squash in a food processor until smooth. Add the bread crumbs, eggs, Parmesan, salt, pepper and nutmeg to the squash and pulse to blend. Transfer the squash to a bowl and stir in the potato.
Butter an 8-inch shallow round baking dish or a 4-cup ring mold and set it in a larger pan. Spoon the flan mixture into the baking dish, smoothing the top. Add enough boiling water to the pan to reach halfway up the side of the dish. Cover the pan with foil and bake for 30 minutes, or until set. Remove the dish from the water bath and let the flan cool slightly. Serve the flan directly from the baking dish or unmold it onto a plate.