HEAT oven to 350°F.
LINE 13x9-inch pan with foil or parchment paper, with ends of foil extending over sides. Mix crumbs and butter; press onto bottom of pan. Top with layers of coconut, nuts, chocolate chips and marshmallows. Drizzle with condensed milk.
BAKE 25 to 30 min. or until golden brown. Meanwhile, melt chocolate squares as directed on package.
DRIZZLE chocolate over dessert; let stand until firm. Use foil handles to lift dessert from pan before cutting into bars.
