1. Preheat oven to 350°F. Wrap outside of a 9-inch springform pan with heavy-duty foil. Lightly spray with non-stick spray.

2. Pulse toasted walnuts in a food processor until finely ground.

3. In a bowl, combine walnut crumbs, graham cracker crumbs, brown sugar, and salt. Stir in melted butter until evenly moistened.

4. Press mixture into the bottom and up the sides of the pan. Bake for 10 minutes. Set aside to cool. Reduce oven temperature to 325°F.

5. In a food processor, blend cream cheese and sour cream until smooth. Add sugar and vanilla. Scrape down sides and beat again.

6. On low speed, add eggs and yolks one at a time. Then mix in maple syrup, maple extract, and heavy cream until just combined.

7. Fold in flour with a spatula until just mixed. Pour filling over crust and smooth the top.

8. Place cheesecake pan in a deep roasting pan. Fill with 2.5 inches of hot water to form a water bath.

9. Bake for 1 hour and 20 minutes. Turn off oven and let sit for 30 minutes with the door closed.

10. Remove from oven. Run a knife around the edge. Cool completely, then chill for at least 6 hours before adding topping.

11. For topping, melt butter over low heat in a skillet. Stir in brown sugar and cook until bubbly, about 2 minutes.

12. Add heavy cream and salt, stir to combine. Fold in toasted walnuts until coated.

13. Remove from heat. Stir in vanilla, maple syrup, and bourbon (if using). Let cool for 10 minutes.

14. Spoon topping evenly over chilled cheesecake. Serve and enjoy.