In a large mixing bowl, combine 1 cup of melted unsalted butter with ½ cup of granulated sugar and ½ cup of light brown sugar. Blend until smooth and creamy, about 2-3 minutes. Then, add 1 large egg and 1 teaspoon of vanilla extract, mixing until fully incorporated.

In a separate bowl, whisk together 2 ½ cups of all-purpose flour, 1 teaspoon of baking soda, and ½ teaspoon of salt. Gradually add into the wet ingredients, stirring gently until combined. The dough will be thick and slightly sticky.

Gently fold in 1 cup of chocolate chips and ½ cup of Halloween sprinkles, ensuring even distribution throughout the dough.

Scoop the dough into balls, about 2 tablespoons each, and place on a lined baking sheet. Cover with plastic wrap and chill in the refrigerator for 1.5 to 2 hours.

Preheat your oven to 350°F (175°C). Arrange the chilled cookie dough balls 2 inches apart on a parchment-lined baking sheet. Bake for 11-13 minutes until edges are golden brown and centers look slightly underbaked.

Gently press a few candy eyes into the warm centers of each cookie once they come out of the oven. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.