In a mixing bowl, combine the melted unsalted butter with light brown sugar and granulated sugar. Stir until smooth and creamy, about 2 minutes. Add the egg and vanilla extract, mixing until fully incorporated.

Gradually add the all-purpose flour, baking soda, and salt to the wet mixture. Mix on low speed until just combined, avoiding over-mixing.

Gently fold in the chocolate chips and Halloween sprinkles into the dough using a spatula.

Scoop tablespoon-sized balls of dough onto a lined baking sheet, spaced about 2 inches apart. Cover with plastic wrap and chill in fridge for 1.5 to 2 hours.

Preheat the oven to 350°F (175°C). Arrange cookie dough balls on parchment-lined baking sheets and bake for 11-13 minutes or until edges are golden.

After removing from the oven, gently press candy eyes onto each warm cookie.

Cool cookies on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely.