Lightly oil a baking sheet. In a dry heavy saucepan cook sugar over moderate heat, stirring with a fork, until melted and cook, without stirring, swirling pan, just until a golden caramel. Add hazelnuts, stirring until coated well. Immediately pour mixture onto baking sheet and cool completely, about 30 minutes. Remove praline from baking sheet and break into pieces. Praline may be eaten as candy or ground in a food processor and used as a dessert topping.