- 70 vanilla wafers (8 1/2 oz), finely ground in a food processor (2 1/3 cups)
- 1 1/4 sticks (10 tablespoons) unsalted butter, melted and cooled
- 20 oz cream cheese (2 1/2 eight-ounce packages), softened
- 8 oz mascarpone cheese at room temperature (about 1 cup)
- 3/4 cup sugar
- 3 large eggs
- 1 teaspoon vanilla
- 1 teaspoon fresh lemon juice
- 1/4 teaspoon salt
- 1 cup sour cream
- 1/4 cup sugar
- 1 teaspoon vanilla
- 1 teaspoon fresh lemon juice
- 1/8 teaspoon salt
- Put oven rack in middle position and preheat oven to 350°F. Butter bottom and side of a 9-inch springform pan.
- Stir together cookie crumbs and butter in a bowl. Reserve 1/4 cup crumb mixture for sprinkling over cheesecake, then pat remainder onto bottom and 1 1/2 inches up side of springform pan (about 1 inch thick). Put pan in a shallow baking pan and bake until golden, about 10 minutes. Cool completely on a rack, about 25 minutes. Leave oven on.
- Beat cream cheese, mascarpone, and sugar in a large bowl with an electric mixer at medium high speed until fluffy, 3 to 5 minutes. Add eggs 1 at a time, beating well after each addition. Add vanilla, lemon juice, and salt and mix at low speed until combined. Pour into cooled crust and bake until cake is set and puffed around edge but still trembles slightly when pan is shaken gently, 25 to 30 minutes. Cool slightly in springform pan on rack, about 20 minutes. (Cheesecake will continue to set as it cools.) Leave oven on.
- Stir together sour cream, sugar, vanilla, lemon juice, and salt in a small bowl and spoon over cheesecake, spreading gently and evenly, leaving a 1/4-inch border around edge.
- Bake cheesecake until topping is set, about 10 minutes. Run a thin knife around edge to help prevent cracking. Sprinkle top with reserved crumbs and cool completely in pan on rack, then chill, loosely covered, at least 8 hours.