Refrigerate frosting mix and whipping cream in small mixer bowl at least 1 hour.
Bake cake mix in 2 round layer pans as directed on package.
Slice strawberries lengthwise; reserve 1/2 cup for garnish.
Split cake to make 4 layers.
Beat frosting mixture until soft peaks form.
Fill layers with 2/3 cup frosting mixture and about 1/2 cup strawberries.
Frost top of cake with remaining frosting mixture; garnish with reserved berries.