Position rack in the center of your oven. Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper. (If you’ll be baking multiple batches, line an additional sheet.)
In a medium bowl, whisk together the white whole wheat flour, all-purpose flour, oats, baking powder, baking soda, salt, cinnamon, ginger, and nutmeg.
In a separate, large bowl, beat together the butter and sugars on medium speed until smoothly combined. Scrape down the sides of the bowl, and beat once more, just until reincorporated.
To the bowl with the butter mixture, add the pumpkin, egg, and vanilla. Beat again, just until evenly blended.
Gradually add the dry ingredients to the wet ingredients, beating on low speed. Stop as soon as the flour disappears.
By hand with a wooden spoon or spatula, fold in the chocolate chips and walnuts.
With a cookie scoop or spoon, scoop the dough by heaping tablespoons so that you have balls that are about 1 1/2-inches each. Leave about 1 inch of space around each cookie (they will not spread much during baking). Place the remaining dough in the refrigerator while the first batch of cookies bakes.
Bake the cookies on the center rack for 11 to 12 minutes, until the edges are lightly browned and the tops feel dry to the touch but the center is still soft underneath. Remove the cookies from the oven, and let them cool on the baking sheet for 5 minutes before transferring to racks to cool completely. Repeat with remaining cookies, ensuring that you always scoop them onto a cooled cookie sheet. Enjoy!
TO FREEZE UNBAKED COOKIES: Place cookie dough balls in a single layer on a parchment-lined baking sheet. Freeze until solid, then transfer frozen cookie dough balls to an airtight freezer-safe storage container for up to 3 months. Bake from frozen as directed, adding extra baking time as needed.
TO FREEZE COOKIES: Transfer fully cooled cookies to an airtight freezer-safe storage container, and freeze for up to 3 months. Thaw and enjoy whenever a craving strikes!
TO STORE: Store cookies in an airtight storage container at room temperature for up to 1 week.