Place 8 tablespoons of the butter and 2 tablespoons of the corn syrup in pan and heat until butter melts. Stir in crackers and mix well. Press mixture into a greased 10-inch spring-form pan. Chill. Melt chocolate with remaining butter, remaining syrup, and vanilla in top of double boiler, stirring occasionally until glossy. Beat cream cheese until smooth, then beat in egg yolks, sugar, and sherry. In separate bowl, sprinkle gelatin over 1/4 cups cold water and leave to soften for 2 minutes. Stand in pan of hot water and stir until dissolved. Cool slightly. Beat egg whites until stiff. Whip cream until it just holds its shape. Stir cooled gelatin into cream cheese mixture in steady stream. Using a large metal spoon, fold in cream then egg whites. Pour mixture into lined pan. Quickly drizzle chocolate sauce over top and swirl with skewer. Chill until set. Cake can be made a day in advance.