Preheat the oven to 325°F (170°C).
Mix graham cracker crumbs with melted butter until combined.
Press the mixture into a 9-inch (23 cm) springform pan, covering the bottom and extending halfway up the sides.
Refrigerate to chill.
In a large bowl, blend cream cheese, sugar, and milk with a hand mixer until fluffy.
Incorporate sour cream, flour, 2 teaspoons bourbon, and eggs, mixing gently until smooth.
Pour the filling over the chilled crust and bake for 1 hour, or until set and no longer jiggles.
In a medium saucepan, mix brown sugar, cornstarch, and salt over low heat.
Whisk in egg yolks, maple syrup, and warm cream until smooth.
Continue cooking on low heat until it thickens like pudding (5-10 minutes).
Remove from heat, add cold butter and remaining bourbon, and whisk until smooth. Cool to room temperature.
Fold in chopped roasted pecans and spread evenly over the baked cheesecake.
Garnish with whole pecans, if desired.
Refrigerate until fully set.
Slice, serve chilled or at room temperature.
