Preheat oven to 325°F
Beat cream cheese, brown sugar, and granulated sugar together in the bowl of an electric mixer fitted with the paddle attachment. Scrape down sides of bowl
Add eggs, one at a time, mixing well after each addition. Scrape down sides of bowl
Whisk together pumpkin purée, cornstarch, cinnamon, and nutmeg in a medium bowl until well combined
Add pumpkin mixture to cream cheese mixture, beating until well combined. Scrape down sides of bowl
Add evaporated milk, mixing well
Slowly pour cheesecake filling onto crust mixture in prepared pan. If you want, drizzle with chocolate syrup.
Place foil-wrapped pan inside a larger roasting pan. Place on oven rack and carefully add enough hot water to reach halfway up sides of springform pan.
Bake 1 hour, or until center moves only slightly when shaken.
Turn oven off. Crack open oven door, and allow cheesecake to cool inside oven 1 hour (this prevents cracking in the surface of the cheesecake).
Remove pan from water bath and set on a wire rack to cool completely (if you cover too early, moisture will collect on the foil and drip onto your cheesecake).
Cover top of pan with foil and refrigerate for at least 4 hours and up to overnight
Remove the side of your springform pan. Slice, and enjoy!