Instructions: Preheat oven to 350 degrees.

Bake potatoes until soft throughout, about 1 hour. Cool, then peel and cut into chunks. Puree in a food processor - do not overmix - and reserve. Reduce oven to 325 degrees.

For caramel, combine sugar and 1/2 cup water in a medium saucepan. Be sure all sugar granules are washed down from pot sides. Cook over moderate heat, swirling pan occasionally, until color is golde-brown and mixture smells like caramel. Often you need to cook it a bit darker than you would imagine. This should take 10 to 15 minutes. Line a 3-quart Pyrex loaf pan with caramel and set aside on a level surface. Add remaining water to caramel in saucepan. Bring to a boil and cook over moderate heat until the sugar dissolves, about 5 minutes. Occasionally stir and brush down sides with a pastry brush dipped in cold water. This process prevents crystallization of the sugar. Set this caramel sauce aside to cool to room temperature, then chill until serving time.

Combine custard ingredients in a large bowl and whisk in the sweet potato puree to combine. Pour through a strainer into lined loaf pan. Place inside a larger roasting pan. Pour in boiling water until it rises halfway up the sides of the loaf pan. Bake about 1 hour and 50 minutes. The center should feel firm when pressed.

Set aside to cool about 1 1/2 hours. Cover with plastic wrap touching top. Refrigerate overnight or as long as 4 days.

Run a knife along inside edge 2 or 3 times to loosen. When you press center, sides should pull away. Cover with a platter and quickly invert. Drain excess caramel into a bowl and strain into reserved cold sauce. Serve slices of flan on dessert plates. Top with chilled caramel sauce.

This recipe yields 10 servings.

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