CRUST:
2 cups graham cracker crumbs (from 14 graham crackers)
2 tablespoons granulated sugar
1/2 cup (1 stick) unsalted butter, melted
FILLING:
1 .25-ounce envelope unflavored gelatin
1 8-ounce bar cream cheese, at room temperature
1 15-ounce can pumpkin puree
1 cup sour cream
3/4 cup granulated sugar
2 teaspoons pumpkin pie spice
1 teaspoon pure vanilla extract
Make the crust: Heat oven to 400° F. In a medium bowl, combine the graham cracker crumbs, sugar, and butter. Transfer to a 9-inch springform pan. Using a straight-sided dry measuring cup, press the mixture into the bottom and 2 inches up the sides of the pan. Bake until set, 8 to 10 minutes. Let cool.
Make the filling: sprinkle the gelatin over 1/4 cup boiling water. Let stand, stirring occasionally, until dissolved, about 5 minutes.
Using an electric mixer, beat the cream cheese until smooth. Mix in the pumpkin, sour cream, sugar, pumpkin pie spice, and vanilla. Mix in the gelatin mixture until incorporated.
Chill: Pour the mixture into the crust and refrigerate, covered, until firm, at least 2 hours and up to 2 days.
Recipe found here.