Put oven rack in middle position and heat oven to 350°F. Whisk together pumpkin, eggs, brown sugar, vanilla, and liqueur (if using) in a bowl until combined. Stir together granulated sugar, cornstarch, cinnamon, nutmeg, ginger, and salt in large bowl. Add cream cheese and beat with an electric mixer at high speed until creamy and smooth, about 3 minutes. Reduce speed to medium, then add pumpkin mixture and beat until smooth. Pour filling into crust, smoothing top, then put springform pan in a shallow baking pan. Bake until center is just set, 50 to 60 minutes. Transfer to rack and cool 5 minutes. (Leave oven on.)