Step 1

Move oven rack to lowest position. Heat oven to 425°F. Lightly grease side only of 9-inch springform pan with shortening.

Step 2

In small bowl, mix graham cracker crumbs, margarine and 2 tablespoons sugar; press evenly on bottom of pan.

Step 3

In large bowl, beat cream cheese, 1 3/4 cups sugar, the flour, orange peel, lemon peel and salt with electric mixer on medium speed about 1 minute or until smooth. Beat in egg product and egg yolks, beating on low speed until well blended. Pour over graham cracker mixture.

Step 4

Bake 15 minutes.

Step 5

Reduce oven temperature to 200°F. Bake 1 hour longer. Cheesecake may not appear to be done, but if a small area in the center seems soft, it will become firm as cheesecake cools. (Do not insert a knife to test for doneness because the hole could cause cheesecake to crack.) Turn off oven; leave cheesecake in oven 30 minutes longer. Remove from oven and cool in pan on wire rack away from drafts 30 minutes.

Step 6

Without releasing or removing side of pan, run metal spatula along side of cheesecake to loosen. Refrigerate uncovered about 3 hours or until chilled; cover and continue refrigerating at least 9 hours but no longer than 48 hours.

Step 7

Run metal spatula along side of cheesecake to loosen again. Remove side of pan; leave cheesecake on pan bottom to serve. Serve with berries, if desired. Store covered in refrigerator.