Preheat your oven to 350°F (180° C). Line a cookie sheet with parchment paper and set it aside. The number of batches will depend on how large/small you want your cookies.
Combine the flour, cornstarch, baking powder, and salt in a medium-sized bowl and set aside.
Cream the butter and sugar together in a large bowl with an electric mixer on medium speed until light in color and fluffy, about 3 minutes. Add cream cheese and vanilla and mix until well combined.
Add the flour mixture to the butter mixture and mix until the dough comes together and is combined.
Add 3 – 4 drops of your chosen food coloring, is using, and mix until well incorporated. Do not overmix.
Form cookie dough into balls, about 1 ½ tablespoon each. For evenly sized cookies, I like to use a small spring-loaded ice cream scoop to spoon out the dough.
Roll cookie dough balls in Halloween sprinkles until completely covered. These cookies don't spread much, so I recommend slightly flattening cookies with your fingers. At this point, you can bake the cookies right away or refrigerate them for up to 3 days.
Bake for 10 -12 minutes, until very lightly colored on top and around the edges. If desired, press 1 or 2 candy eyeballs into the freshly baked cookies. Allow to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.