Position an oven rack in the lower 1/3 of the oven and preheat to 350 degrees F.
Put 1/2 of the chocolate chips, hazelnuts, and flour in the bowl of a food processor. Pulse until the hazelnuts are coarsely chopped. Pour the hazelnut mixture into a small bowl and set aside. Combine remaining chocolate chips and sugar in the food processor. Blend until the mixture is finely ground. With the machine running, gradually add the hot water until the chocolate is melted and mixture is smooth. Add the eggs, butter, vanilla and cinnamon. Pulse until mixture is blended. Return the hazelnut mixture to the food processor and pulse to incorporate. Pour the mixture into a buttered and floured 9-inch pie dish. Bake for 35 minutes. Place the pie on a cooling rack and cool for 1 hour. (Top may crack during cooling.) Refrigerate for 2 hours. (Pie can be made 1 day in advance and stored in the refrigerator). Allow the pie to return to room temperature for 30 minutes before serving.
In a large mixing bowl, beat the cream until it forms soft peaks. Add the powdered sugar, vanilla, and cinnamon. Continue to beat until cream holds stiff peaks.
To serve: Cut the pie into slices and dollop with the Vanilla Cream.
Recipe courtesy of Giada De Laurentiis, 2008