This dessert gets well-rounded chocolate richness from three sources: chocolate graham crackers in the crust, plus intense cocoa powder and luscious milk chocolate in the filling.
Preheat oven to 350°.
To prepare crust, spread oats on a baking sheet. Bake at 350° for 10 minutes or until lightly browned, stirring after 5 minutes. Cool. Combine oats, crackers, brown sugar, and 1/8 teaspoon salt in a food processor; process until finely ground. Add butter and egg white; process until moist. Press mixture into bottom and 1 1/2 inches up sides of a 9-inch springform pan coated with baking spray. Bake at 350° for 22 minutes. Cool completely on a wire rack.
Reduce oven temperature to 325°.
To prepare the filling, sift together granulated sugar, cocoa, flour, and 1/4 teaspoon salt.
Place cheeses in a large bowl; beat with a mixer at medium speed until smooth. Add eggs, 1 at a time, beating well after each addition. Add vanilla and chocolate, beating at low speed just until combined. Sprinkle sugar mixture over top of cheese mixture; beat at low speed until combined. Fold 1 cup whipped topping into mixture. Pour mixture into prepared pan, smoothing top. Bake at 325° for 1 hour or until cheesecake center barely moves when pan is touched. Remove cheesecake from oven; run a knife around outside edge. Cool to room temperature. Cover and chill 8 hours or overnight. Slice cheesecake into 14 slices; top each serving with about 1 tablespoon whipped topping. Divide berries among servings.