In a large bowl, whisk together flour, oats, baking powder, corn starch, cinnamon and ginger
In a separate bowl using a hand or stand mixer, combine butter, white and brown sugars until light and fluffy
Add egg and vanilla and mix well
Add in half of flour mixture to the butter mixture and stir until just combined.
Add in half of butternut squash puree and stir until just combined.
Repeat process until all flour and puree is incorporated into the batter.
Fold in raisins
Chill dough in refrigerator for 2 hours, or until dough is completely chilled throughout
Preheat oven to 350 F
Line a large baking sheet with parchment paper
Using a cookie or ice cream scoop, spoon dough into ball shapes and place cookies on baking sheet roughly 2 inches apart
Bake for 14-15 minutes
Allow to briefly cool on pan before transferring to a wire cooking rack
Complete process until all cookies are baked, but do not overcrowd oven with multiple baking sheets at one time