To make the crust:
In the bowl of an electric mixer fitted with the flat beater, combine the butter, granulated sugar, all-purpose flour, rice flour, cocoa powder and salt. Mix on low speed until the dough comes together. Roll out the dough into a 9-inch round. Pat the dough into the bottom of a 9-inch springform pan. Refrigerate for at least 30 minutes or as long as overnight.
2Preheat an oven to 300°F (150 degrees C)
Bake the crust for 30 minutes. Let cool completely.
3To make the cheesecake:
Have a pot of hot water ready. In the bowl of an electric mixer fitted with the flat beater, beat the cream cheese on medium speed until smooth. Add the granulated sugar and beat until smooth. Add the eggs 1 at a time, beating well after each addition. Stir in the sour cream, the espresso powder, the Irish whiskey (or Irish cream liqueur, if using), and mix until smooth.
4Spread the batter evenly over the crust. Place the springform pan in a large roasting or baking pan, then place on the oven rack. Carefully fill the roasting pan halfway with hot water. Bake for 1 1/4 to 1 1/2 hours. To test for doneness, gently shake the pan; the cheesecake should be set from the center to the edges but not dry.
Transfer the pan to a wire rack and let cool for 30 minutes, then refrigerate until chilled throughout, about 1 hour
5To make the caramel glaze:
In a small, heavy saucepan over low heat, combine the brown sugar, butter and cream. Heat until the sugar dissolves, then increase the heat to high and bring to a boil. Reduce the heat to medium and cook, stirring constantly, until thick and smooth, add the Irish whiskey (or Bailey's Irish Cream, if using). Let cool to room temperature.
6Caramel Glaze and Garnish: (Optional)
Drizzle slices with the caramel glaze and chocolate syrup and dust slices with cocoa powder. Serve with a dollop of whipped cream.