Stir together first 3 ingredients; press mixture onto bottom of a 10-inch springform pan.
Beat cream cheese at medium speed with an electric mixer until smooth; add eggs, 1 at a time, beating until blended after each addition. Add 1 1/2 cups eggnog, and beat until blended. Fold in 2 cups powdered sugar and 2 Tbsp. flour; carefully pour cream cheese mixture into prepared pan.
Bake at 325° for 1 hour. Turn off oven. Let cheesecake stand in oven, with door closed, 1 hour. Remove to wire rack, and let cool completely. Cover and chill at least 8 hours.
Beat whipping cream at high speed with an electric mixer until stiff peaks form; fold in remaining 1/2 cup eggnog. Spread mixture evenly over top of chilled cheesecake, and garnish, if desired.