In a large bowl, combine sugars and shortening. Beat until creamy. Beat in eggs and vanilla. Gradually add flour, soda, and salt. Stir in nuts, chocolate chips, and marshmallows. Spread into a greased cookie sheet. Bake at 375 for 20 minutes. Cut in 2-inch squares.
Recipe by Amish 365 at https://www.amish365.com/more-bars-chocolate-chip-marshmallow-bars/