1 1/4 pounds yellow or red yams
1 1/2 cups granulated sugar
3/4 cup water
8 eggs
2 egg yolks
1 (14 ounce) can sweetened condensed milk
1 cup heavy cream
1 cup half and half
1 1/2 teaspoons vanilla extract
1/2 teaspoon ground cinnamon
1/2 teaspoon ground allspice
1/2 teaspoon ground nutmeg

Preheat the oven to 325 degrees F.

Wash the yams and bake for 1 to 1 1/2 hours, until they are soft. Remove yams from the oven, then peel, cut into chunks and pur? in a blender. There should be 1 1/2 cups of pur?. Set aside to cool.

While the yams are baking, prepare the caramel. In a small, heavy saucepan, bring the sugar and 1/4 cup of the water to a boil over high heat, washing down any crystals clinging to the sides of the pan with a pastry brush dipped in cold water. Watch the syrup carefully, not stirring, and when it turns golden brown and is bubbling furiously, pour it into the center of an aluminum or glass 9-inch flan pan or souffl?dish, swirling the syrup around the bottom and partially up the sides of the pan. Pour any remaining syrup that does not adhere back into the pot, add the remaining 1/2 cup of water, and bring the syrup back to a boil to serve with the flan. Set aside.

Beat the eggs and yolks in a bowl until light and fluffy. Add remaining ingredients, along with the cooled yam puree, and beat well. Pour mixture into the prepared pan, place it in a roasting pan, and pour boiling water into the roasting pan so it comes halfway up the sides of the flan. Bake for one hour or until firm throughout. Do not overbake.

Remove from the water bath, cool to room temperature, and then chill. To unmold, run a knife around the edge of the flan, place a serving plate over the flan, and invert, rapping it on the counter to loosen the flan. Pour off any juice and serve with the caramel sauce.

The flan can be made up to 4 days in advance and kept in the refrigerator, tightly covered with plastic wrap.