In a medium mixing bowl whisk together the flour, pumpkin pie spice, cinnamon, baking powder, baking soda and salt. Set aside.

In a large mixing bowl combine the butter and sugar and beat on medium-high until lightened and fluffy. Add the pumpkin puree, eggs and vanilla and beat on medium until combined. Scrape down the sides and bottom of the bowl, then mix again. Add the flour mixture in four additions beating well after each addition. Scrape down the sides of the bowl and blend again.

Add the chocolate chips and walnuts and fold together with a spatula until blended.

Using a small cookie scoop, place dough balls on the prepared baking sheet, at least 1-inch apart. The cookie dough will not spread so feel free to gently flatten out the cookie rounds to the desired size.

Bake cookies for 14 to 18 minutes or until the edges are lightly browned. Cool on the baking sheet for 2 minutes, then remove to a wire rack to cool completely. Once cooled, drizzle or spread each cookie with icing.

Whisk together the sugar, milk and vanilla until smooth. Drizzle the icing over the cooled cookies. Allow the icing to dry before storing the cookies. If desired, add more powdered sugar or milk to achieve desired consistency. Thicker icing can be spread on each cookies instead of drizzling.

Store in an airtight container at room temperature. Cookies will keep for up to 5 days. Cookies can also be frozen.