Stir together ground hazelnuts and butter. Press the mixture onto the bottom of a 9-inch springform pan.
In a large mixing bowl, combine the cream cheese, sugar, vanilla, and almond extract; beat until fluffy. Add the eggs all at once and beat on low speed until just combined. Stir in the chopped hazelnuts and the 1/4 cup liqueur.
Turn the cream cheese mixture into the prepared pan. Bake in a 350 degree F oven for 1 hour or until the center appears nearly set when gently shaken. Cool for 15 minutes in pan on wire rack.
Loosen from side of pan. Cool for 30 minutes more. Remove side of the pan. Cool. Chill the cheesecake at least 4 hours before serving.
Beat whipping cream with the 2 tablespoons hazelnut liqueur. Serve the flavored whipped cream with the cheesecake. Makes 16 servings.
You can use almonds instead of hazelnuts and substitute amaretto for the hazelnut liqueur, if you like.