In a mixing bowl, beat together the butter and cream cheese until smooth and creamy. Gradually add sugar, mixing until light and fluffy.

Blend in the egg and vanilla until well combined.

In a separate bowl, whisk together flour, cornstarch, baking powder, and salt. Gradually incorporate this mixture into the wet ingredients.

Wrap the dough in plastic wrap and chill in the refrigerator for at least 2 hours.

Preheat your oven to 350°F (175°C). Roll out the chilled dough and cut out ghost shapes.

Chill the cookie cutouts in the refrigerator for 15 minutes.

Bake for 12–14 minutes, until set but slightly soft in the center. Let cool on a wire rack.

Prepare the buttercream frosting by beating butter until creamy. Gradually mix in powdered sugar, vanilla, and cream.

Frost the cooled cookies, sprinkle with sanding sugar, and add sprinkles for eyes and mouth.