Combine 2 cups sweet biscuit crumbs, 1/2 cup white sugar, 1 teaspoon cinnamon and melted butter or margarine. Press firmly into the bottom of a 23cm springform pan.
In a large bowl, blend the cream cheese and 1 1/4 cup white sugar with an electric mixer at medium speed until well blended. Add the eggs, one at a time, blending well. Add vanilla essence. Add 1/2 cup liqueur and blend for 5 minutes. Pour the filling on top of the crust.
Preheat the oven to 180 degrees C. Bake for approximately 1 hour. The cake should be golden brown and will have risen to the top of the pan. Turn off the heat and let cool in the oven for 2 1/2 hours. When cool, remove the rim of the springform pan.
In a small bowl, mix the sour cream, icing sugar and 1 teaspoon liqueur together. Spoon onto the top of the cooled cheesecake.
In a small bowl, combine the finely ground pecans, finely ground sweet biscuit crumbs, 1 1/2 tablespoons white sugar and cinnamon. Sprinkle the pecan topping on the cheesecake and carefully press into the sides. Garnish the top and sides with pecan halves.