In the bowl of a stand mixer fitted with a paddle attachment, cream butter and brown and granulated sugar together on medium speed, beating until light and fluffy about 3 minutes. Add in egg and vanilla and mix until incorporated on low speed. Turn the mixer up to medium-high and mix for 1 minute.

Scrape down the sides of the bowl if needed. Add the cornstarch, baking soda, and salt. Mix for 30 seconds then add the flour 1 cup at a time. Mix until fully incorporated.

Add the chocolate chips and either beat for a few seconds on low speed or fold in by hand.

Scoop about 2 tablespoons of the dough into balls. Add the Halloween sprinkles to a small bowl and holding the bottom of the dough ball press the top of the dough ball into the sprinkles. If needed, press more sprinkles into the dough. Top with more chocolate chips if desired. Cover with plastic wrap and chill the dough for 2 hours in the fridge.

When ready to bake, preheat oven to 350 F. Place cookie dough on baking sheets lined with parchment paper, spaced 2 inches apart. Bake for 5 minutes, remove from oven and top with the desired amount of candy eyes. Then place back in the oven and bake for another 3 to 5 minutes. (8-10 minutes total) Don't over bake, the cookies will set up as they cool.

Remove from oven, let cool on baking sheet for 5-10 minutes, and then transfer to a wire rack to finish cooling. (Store in an airtight container.)