Position a rack in the middle of the oven and preheat to 350 degrees . Wrap the outside of a 9-inch springform pan with heavy-duty foil. In a medium bowl, stir together the gingersnap crumbs and butter. Press the mixture evenly in the bottom of the prepared pan and bake for 10 minutes. Remove from the oven and lower the temperature to 325 degrees . Sprinkle the hot crust evenly with the chocolate chips and let cool.
Meanwhile, using an electric mixer, beat together the cream cheese, 3/4 cup sugar, the vanilla and salt at medium speed until fluffy, about 3 minutes. Scrape the sides and bottom of the bowl. Gradually mix in the egg and egg whites, scraping the bowl again. Mix in 1 cup sour cream. Turn off the machine and, using a spatula, stir in 1/2 cup ginger.
Pour the batter into the crust. Place the wrapped pan in a roasting pan and fill the roasting pan with warm water to a depth of 1 inch. Bake until the cheesecake is just set, about 50 minutes. Transfer the cake to a rack, remove the foil and let the cheesecake cool completely. Cover and refrigerate until chilled, 4 hours or overnight.
In a small bowl, combine the remaining 1 tablespoon sugar and 1 cup sour cream, stirring to dissolve the sugar. Remove the sides of the springform pan and spread the sour cream mixture on top. Sprinkle the remaining 2 teaspoons ginger in the center. Serve cold.