Prepare the Crust

1. Preheat the oven to 325°F (170°C).
2. In a medium bowl, mix graham cracker crumbs with melted butter until well combined.
3. Press the mixture into the bottom and halfway up the sides of a 9-inch springform pan. Place in the fridge to chill while preparing the filling.

Make the Cheesecake Layer

1. In a large mixing bowl, beat the cream cheese, sugar, and milk until smooth and fluffy.
2. Add sour cream, flour, bourbon (if using), and eggs, mixing gently until just combined.
3. Pour the cheesecake filling over the chilled crust. Bake for about 60 minutes, or until the cheesecake is set but still slightly wobbly in the center. Let cool on a wire rack.

Prepare the Pecan Pie Topping

1. In a saucepan, combine brown sugar, cornstarch, and salt. Whisk in egg yolks, maple syrup, and warm cream over low heat.
2. Cook, stirring frequently, until the mixture thickens to a pudding-like consistency (about 8-10 minutes).
3. Remove from heat, add cold butter, and whisk until smooth. Fold in chopped pecans.
4. Once the cheesecake has cooled, spread the pecan topping evenly over the cheesecake. Garnish with whole pecans, if desired.

Chill and Serve

1. Refrigerate the cheesecake for at least 4 hours (or overnight) until fully set.
2. Slice and serve chilled, optionally with a dollop of whipped cream or caramel drizzle.