In a medium bowl, whisk together the flour, baking soda, kosher salt, and pumpkin pie spice. Set aside.
Melt the butter and let it cool for a few minutes. Add it to a large bowl with the brown sugar and granulated sugar, and whisk until smooth.
Whisk in the pumpkin purée until combined. Add the egg yolk and vanilla, and whisk until smooth.
Add the dry ingredients to the wet ingredients, half at a time. Stir with a spatula until no flour streaks remain. Fold in ¾ cup of the chocolate chips.
Cover the bowl and chill the dough for 1 hour.
Preheat the oven to 350 degrees F. Line two baking sheets with parchment paper or silicone baking mats.
Use a 2-tablespoon cookie scoop (size #40) to portion the dough onto the prepared pans, 8 cookies per pan, leaving 2 inches between each. If you don't have a scoop, roll the dough into balls of about 2 tablespoons each. Press a few extra chocolate chips from the remaining ¼ cup onto the top of each cookie.
Bake for 10 to 12 minutes, swapping racks and rotating the pans halfway through, or baking in batches. The cookies are done when the edges are set and the tops are no longer shiny. The centers will still be soft.
Let the cookies rest on the pans for a few minutes before transferring to a wire rack to cool completely.