½ cup plus 2/3 cup sugar
2 cups milk
¼ cup coarsely ground coffee beans
2 large eggs
4 large egg yolks
¼ teaspoon freshly grated nutmeg
1 teaspoon cinnamon
1½ cups cooked kabocha purée
Preheat the oven to 350°.
In a small saucepan, combine ½ cup sugar with ¼ cup water.
Cook over medium heat until the sugar has dissolved. As the sugar begins to color, swirl the saucepan around to caramelize the sugar evenly. Cook until the syrup turns a honey-caramel color. Remove from heat and carefully (the sugar is very very hot!) pour the caramel into a 9-inch glass pie pan. Tilt the pan so that the caramel coats the bottom. Allow caramel to cool and harden.
In a small saucepan, bring the milk and coffee beans to a boil. In a heatproof bowl, whisk the eggs, egg yolks, 2/3 cup sugar, nutmeg and cinnamon until blended. Add kabocha and mix until blended.Whisking constantly, slowly pour the hot milk in a thin stream into the egg mixture. Strain through a fine-meshed sieve and pour into the caramel-coated dish.
Place the pie dish in a larger, ovenproof pan with sides that are as high as the pie dish. Place pan with pie dish in oven and fill pan with enough hot water to reach 2/3 up the side of the dish. Bake until a knife inserted into the center of the custard comes out clean (though the custard will still be wobbly), about 40 minutes. Remove dish from water bath and transfer to a rack to cool to room temperature. (Flan can also be covered and refrigerated overnight.)
To serve, run the tip of a knife around the top of the custard to loosen it. Invert a serving platter over the pie pan and quickly turn it over again. Carefully remove the pie pan. Serves 6–8.