Preheat oven to 350°F (180°C). Line an 8-inch (20cm) springform pan with parchment paper. Make a collar around the pan using a strip of buttered parchment paper extending above the rim. Blend gingersnaps with butter; press into bottom of pan. Bake for 8 minutes.
Filling: Increase oven to 450°F (230°C). Beat cream cheese until smooth. Add sugar and beat until combined. Beat in juice, brandy, vanilla and nutmeg. Beat in eggs, one at a time, until combined; scrape onto crust. Bake for 15 minutes. Reduce oven to 200°F (100°C); bake for 1 hour. Cool cake, tented with foil in oven with door ajar for 1 hour. Chill completely, about 1 hour.
Sauce: Stir sugar with corn starch in a saucepan. Stir in water, brandy, butter and juice. Cook on medium for 5 minutes, stirring, or until thickened. Stir in raisins. Serve warm over cheesecake.