Preheat oven to 350°F. Grease a 9-inch springform pan.
In a medium bowl, combine the butter, graham cracker crumbs, and 3 tablespoons sugar. Press into the bottom of the prepared pan.
In a large bowl, beat cream cheese until smooth. Gradually beat in 1 1/2 cups sugar and salt. Beat in eggs one at a time. Add vanilla and mascarpone cheese; mix well.
Pour batter into prepared pan.
Bake for 40 minutes or until center is almost set.