Process graham crackers and 1/2 cup hazelnuts in a food processor until finely ground. Add melted butter; pulse 4 or 5 times or until blended. Press mixture into bottom and 1 1/2 inches up sides of a 10-inch springform pan; freeze 15 minutes. Carefully spread melted mini-morsels over frozen crust. Freeze 15 minutes.
Meanwhile, beat cream cheese and softened butter at medium speed with an electric mixer just until smooth. Add melted white chocolate, beating just until blended.
Add eggs, 1 at a time, and yolk, beating just until blended after each addition. Stir in toffee bits and next 4 ingredients. Pour batter into prepared crust.
Bake at 325° for 1 hour and 15 minutes or until almost set.
Meanwhile, combine sour cream, sugar, and 1 tablespoon liqueur in a medium bowl. Remove cheesecake from oven; carefully spoon sour cream mixture evenly over cheesecake.
Bake 15 more minutes; remove from oven. Run a knife around edge of pan, and release sides. Cool completely on a wire rack. Cover and chill 8 hours. Serve with sweetened whipped cream, toffee bits, and hazelnuts. Store in refrigerator.
Tip: There are 8 cups of batter for this stately cheesecake. Once the sour cream mixture is added, the pan will be very full, so be careful when transferring to and from the oven.