Heat oven to 350°F. Place hazelnuts on ungreased cookie sheet. Bake at 350°F. for 5 to 8 minutes or until lightly browned and skins have loosened. Turn hazelnuts onto clean, cloth towel; rub nuts between towel to remove skins. Cool 10 minutes. Finely chop nuts.
In medium saucepan, combine semisweet chocolate, bittersweet chocolate and half-and-half. Cook over low heat until chocolate is melted, stirring occasionally; beat with whisk or mixer until mixture is smooth and has cooled to room temperature.
Add butter 1 tablespoon at a time, beating until smooth and creamy. Add liqueur 1 tablespoon at a time, beating until well blended. Cover; refrigerate 2 hours or until mixture is chilled and thick, stirring once or twice.
Spread chopped nuts in pie pan. Drop chocolate mixture by teaspoonfuls onto nuts; gently roll to coat with nuts. Balls may be slightly rough and irregular in shape. Place in paper candy cups, if desired. Store in tightly covered container in refrigerator for up to 1 month or in freezer for up to 6 months.