Preheat oven to 350°. Combine first 3 ingredients. Press into a greased 9 x 13 pan. Bake 8 minutes; remove from oven. Meanwhile, in a large bowl beat cream cheese and sugar with an electric mixer on medium until combined. Gradually beat in eggs and milk. Reserve 1 cup mixture and add to a separate bowl; combine with cheese ball mix. Pour remaining cream cheese mixture over crust, spreading evenly. Drizzle cheese ball mixture over top; gently swirl with a knife or toothpick to create a marbled effect. Bake 30-35 minutes or until a knife inserted in the center comes out clean. Cool slightly; cover and chill until served. Garnish with fresh blackberries, if desired. Makes 16 servings.