In a mixing bowl, combine 1.5 cups of crushed graham cracker or gingersnap crumbs with 0.33 cups of sugar and 0.5 cups of melted butter. Mix until the texture resembles wet sand. Firmly press this mixture into the bottom of a 9-inch springform pan to create an even crust. Place the pan in the freezer for 15 minutes.

Using a hand mixer, whip 16 ounces of softened cream cheese in a large bowl until smooth and creamy, about 2-3 minutes. Gradually add 1 cup of canned pumpkin, 1 cup of powdered sugar, 2 tablespoons of molasses, 1 teaspoon of vanilla extract, and 1.5 teaspoons of mixed spices. Blend until silky smooth.

In a separate bowl, pour 1 cup of heavy cream and use a hand mixer to whip until stiff peaks form, usually 3-5 minutes. Gently fold the whipped cream into the pumpkin mixture, being careful not to deflate the cream.

Carefully pour the creamy pumpkin filling into the chilled crust, using a spatula to smooth the top for an even finish. Cover the springform pan with plastic wrap and refrigerate for at least 8 hours, ideally overnight.

After chilling, remove from the fridge, unclip the springform pan, and serve cold. Garnish with whipped cream, caramel, or crushed cookies if desired.