Preheat oven to 350℉. Grease and flour two 9" round layer cake pans and set aside.

In a large bowl, combine cake mix, 1¼ cups water, oil, and egg whites and blend.

Beat two minutes at high speed. Fold in the finely chopped white chocolate chips.

Pour into prepared pans and bake at 350℉ for 25-35 minutes until toothpick inserted in cake comes out clean.

Cool on wire rack for 15 minutes, then remove from pans and cool completely on wire rack.

Filling

For filling, beat cream cheese, ⅓ cup maple syrup, and vanilla extract in small bowl until smooth.

Beat whipped cream and 2 tablespoons powdered sugar until stiff and fold into cream cheese mixture.

Refrigerate while preparing frosting and glaze.

Frosting

For frosting, beat together 2 cups powdered sugar, ½ cup softened butter, 2 tablespoons maple syrup, and enough milk for a smooth spreading 

Glaze

For glaze, in small saucepan heat together 1 cup white chocolate chips with 2 tablespoons milk, stirring constantly until smooth. You may need to add more milk for a pouring consistency.

Set this pan in a bowl of hot water to keep warm. 

Assembly

Place one cake layer upside down on serving plate.

Top with all of the maple filling. Place remaining cake layer, right side up, on top of maple filling.

Pour white chocolate glaze over top of cake, spreading gently if necessary to cover top.

(If some glaze drips down sides of cake, that's ok; the glaze should be stiff enough so it moves very slowly.)

Frost sides of cake with the frosting. Store cake in refrigerator.