Preheat oven to 350°F (175°C).

Spread hazelnuts in a single layer on a baking sheet.

Bake for 15 minutes, or until skins split.

Transfer hazelnuts to a colander.

Rub briskly with a kitchen towel to remove skins; discard skins.

Finely chop the hazelnuts.

Combine 1/2 cup chopped hazelnuts, graham cracker crumbs, and melted butter in a bowl.

Mix well.

Press mixture firmly into the bottom and up the sides of a buttered 9-inch pie plate.

Bake at 375°F (190°C) for 7 minutes, or until lightly browned.

Cool completely on a wire rack.

Spoon softened vanilla ice cream into the cooled crust.

Cover and freeze until almost firm.

Place sugar in a large heavy skillet.

Cook over medium heat, stirring constantly with a wooden spoon, until sugar melts and turns golden (about 20 minutes).

Add remaining 1/2 cup chopped hazelnuts to the melted sugar and stir well.

Working quickly, pour mixture into a 15x10x1 inch jelly roll pan lined with aluminum foil.

Spread in a thin layer.

Cool completely.

Coarsely break hazelnut praline candy into pieces.

Reserve 1 cup of praline candy pieces for garnish.

Crush the remaining candy pieces.

Fold crushed candy into softened chocolate ice cream.

Spread chocolate ice cream mixture over vanilla ice cream layer.

Cover and freeze for at least 8 hours, or until firm.

Top each serving with reserved praline candy pieces.

Add a splash of Frangelico if desired.