3/4 cup finely crushed chocolate wafers (about 13)
2 tablespoons butter, melted
6 ladyfingers, split lengthwise
1 teaspoon instant espresso coffee powder or instant coffee crystals
2 tablespoons rum, brandy or milk
2 8-ounce packages cream cheese, softened
1 8-ounce carton mascarpone cheese, softened, or one 8-ounce packaged cream cheese, softened
1 cup sugar
1 tablespoon cornstarch
1 teaspoon vanilla
1 8-ounce carton dairy sour cream
Grated semisweet chocolate (optional)
For crust, combine wafers and butter. Press onto the bottom of an ungreased 9" springform pan. Cut the split lady fingers in half crosswise, line sides of pan with ladyfinger pieces, with rounded side out and cut side down. Set pan aside.
Preheat oven 350°F
For filling, dissolve coffee powder or crystans in rum, brandy, or milk (there's no need to heat the liquid to dissolve powder or crystals); set aside. Beat cream cheese and mascarpone or cream cheese in a medium mixing bowl till combined. Gradually add sugar, beating on medium to high speed till smooth. Beat in cornstarch and vanilla. Add eggs all at once. Beat on low speed just till combined. Stir coffee mixture into cheese mixture.
Pour filling into crust-lined pan. Place springform pan in a shallow baking pan. Bake in the preheated oven for 45 to 50 minutes or till center appears nearly set when gently shaken. Remove from oven. Immediately stir sour cream; gently spoon sour cream on top of hot cheesecake, carefully spreading to within an inch of edge.
Cool in springform pan on a wire rack for 15 minutes. Use a narrow metal spatula to carefully loosen lady fingers from sides of pan. Cool 1 hour. Cover and chill in the refrigerator at least 4 hours. If desired, sprinkle grated chocolate over top before serving.