Heat oven to 350°F. Line cookie sheet with cooking parchment paper.
Remove dough from package; knead in red and yellow colors until dough is desired shade of orange. Shape dough back into original log shape; cut into 18 slices. On cookie sheet, place slices 2 inches apart.
Bake 6 to 10 minutes or until set. While still warm, cut cookies with 3-inch pumpkin-shaped cookie cutter. In 6 of the cookies, use small round cookie cutter to cut out center of pumpkin. Gently remove cutout portion of cookie. Cool 5 minutes; remove from cookie sheet to cooling rack. Cool completely.
In small bowl, mix powdered sugar, milk, corn syrup and vanilla with whisk until smooth. Tint with green food color. Spoon icing into decorating bag fitted with small round tip or small resealable food-storage plastic bag with tiny corner cut off.
For each sandwich cookie, pipe green icing around top edge of 1 whole pumpkin cookie. Top with 1 pumpkin cookie with cutout center; pipe green icing around edge of pumpkin. Fill hole in center with chocolate chips. Top with second whole pumpkin cookie. Pipe green icing on stem of top pumpkin cookie.