Grind hazelnuts in a food processor until fine.
Bring cream to a boil in a medium saucepan over medium-high heat, being careful to boil over. Add the sugar and stir until it is dissolved. Sir in the hazelnuts, bring back to a boil, and remove from the heat. Cool nearly to room temperature. Heat oven to 325 F.
IN a large bowl, bean together the egg and egg yolks until smooth. Slowly add the cream mixture, stirring constantly. Stir in the Frangelico. Strain the mixture through a fine sieve into a large glass measuring cup with a spout, pressing against he mesh to extract all the flavor form the nuts. Discard the nuts.
Pour mixture into 4 - (4oz) pots de creme cups (many pot de creme cups are 3 ounces so it make one more serving) or 4 oz ramekins. Arrange in a deep baking dish.
Pour hot tap water into the baking dish so that it comes within 1/2 inch of the top of the pots. Do not get water in the pots de creme cups. Cover the dish with a sheet of aluminum foil. Put the baking dish in the oven and bake, until the custards are just set in the centers, approximately 33 to 35 minutes. Do not overbake.
Carefully remove pots from the water and allow to cool to room temperature. If you are using pots de creme cups, put the lids on the pots. Refrigerate at least one hour, up to overnight.
Serve
If pots de creme have been chilled for several hours then make sure to allow them to warm for at least 20 minutes before serving.
Use a truffle/chocolate shaver (or good vegetable peeler) to shave chocolate curls. Scatter curls atop each pot de creme.