For crust, combine crushed graham crackers, crushed gingersnaps, the 2 tablespoons pecans, flour, powdered sugar, and melted butter or margarine in a medium bowl. Press evenly onto the bottom of a 9-inch springform pan; set aside.
Beat cream cheese and granulated sugar in a large mixing bowl with an electric mixer on medium speed until fluffy. Add the 3 eggs all at once, beating on low speed just until combined.
Place 1 cup of cream cheese mixture in a medium bowl. Add pumpkin, the 1 egg, milk, cinnamon, ginger, and nutmeg. Beat on low speed just until combined. Pour pumpkin mixture into prepared springform pan. Top with cream cheese mixture. With a knife or thin metal spatula, gently swirl through the layers to marble.
Place springform pan in a shallow baking pan. Bake in a 350 degree F. oven for 40 to 45 minutes or until center appears set when shaken. Cool on wire rack 15 minutes. Loosen crust from sides of pan. Cool 30 minutes more; remove sides of pan. Cool completely. Cover; chill at least 4 hours.
Before serving, beat whipping cream until stiff peaks form. Pipe or spoon into mounds atop cheesecake. Garnish with toasted chopped pecans. Makes 12 to 16 servings.
Refrigerate, covered, up to 1 week, or freeze up to 1 month. Thaw overnight in refrigerator before serving.