Preheat the oven to 350°F. Line two large baking sheets with parchment paper (or spray with nonstick cooking spray) and set aside.

In a bowl, stir together the flour, pumpkin spice, and baking soda, and set aside.

Slowly add the flour mixture and mix until combined (scraping down the sides as needed).

Stir in the old fashioned oats and mix until evenly distributed. Note: he mixture will be very thick.

Using a 1.5 tablespoon cookie scoop (or just use a large spoon) dollop the cookie dough balls onto the prepared sheet trays about 2 inches apart.

Bake in the middle rack of the oven for about 11-13 minutes until they puff slightly, appear dry on top, and are lightly golden around the edges.

Allow the cookies to cool on the trays for about 2 minutes before transferring to a wire rack to cool completely.

While the cookies are cooling, make the frosting. In a medium bowl, mix together the softened butter until smooth.

Slowly add the powdered sugar a little at a time until all the powdered sugar is added and it resembles course sand.

Add 3 Tablespoons of the heavy cream along with the vanilla extract and pumpkin pie spice. Mix until combined. If it still seems too thick, add an additional Tablespoon of heavy cream.

Once everything is mixed in, turn the mixer up to high and mix for about 3 minutes until light and fluffy.

Once the cookies are completely cool, spread the frosting on top of each of them. I find this easiest to do with an offset spatula but a butter knife works just fine as well.

Optional: sprinkle the tops with a little more pumpkin pie spice then serve!