Preheat oven to 350 degrees F Prepare pan: 9-inch cheesecake pan, ungreased, or springform pan with 3-inch sides, greased.
Crust: In a medium bowl, combine graham cracker crumbs, almonds and butter. Press into bottom of cheesecake pan and freeze.
Filling: In a large mixer bowl, beat cream cheese, butter and sugar on medium-high speed for 3 minutes. Add eggs, one at a time, beating after each addition. Mix in sour cream, orange zest, orange juice concentrate and vanilla extract. Fold orange segments into batter. Pour over frozen crust. Bake in preheated oven for 45 to 55 minutes or until the top is light brown and the center has a slight jiggle to it. Cool on the counter for 10 minutes (do not turn the oven off). The cake will sink slightly.
Topping: In a small bowl, combine sour cream, sugar and orange juice. Pour into center of cooled cake and spread out to edges. Bake for 5 minutes more. Cool on a rack for 2 hours. Cover and refrigerate for at least 6 hours before decorating or serving.
Decoration: In a well-chilled bowl, whip cream on medium-high speed until soft peaks form. With the mixer still running, sprinkle sugar into cream and continue whipping until firm peaks form. Ice top of cake or pipe a border around cake, if desired.
Tips: Fresh mandarin oranges are usually available in November and December for the peak holiday baking season. Store in the refrigerator as they spoil quickly, and wash well before zesting.
Yield: 10 to 12 servings
Source: E-Cookbooks.net