Stir together first 3 ingredients; press mixture into bottom of a lightly greased 9-inch springform pan.
Bake crust at 325° for 10 minutes. Cool on a wire rack. Reduce oven temperature to 300°.
Beat cream cheese, 1 cup sugar, and 3 tablespoons flour at medium speed with an electric mixer until smooth. Gradually add vanilla and Irish cream liqueur, beating just until blended. Add eggs, 1 at a time, beating at low speed just until blended after each addition. Add 3/4 cup sour cream, beating just until blended.
Pour half of batter into prepared crust. Dollop strawberry preserves over batter; gently swirl batter with a knife to create a marbled effect. Top with remaining batter.
Bake at 300° for 55 minutes or until edges of cheesecake are set. (Center of cheesecake will not appear set.) Turn off oven; let cheesecake stand in oven 15 minutes. Remove cheesecake from oven; gently run a knife around edge of cheesecake to loosen. Cool completely on a wire rack. Cover and chill 8 hours.
Release and remove sides of pan. Spread remaining 1/2 cup sour cream evenly over top of cheesecake; garnish, if desired.
Note: For testing purposes only, we used Baileys Irish Cream.