In a mixing bowl, cream together unsalted butter, cream cheese, and granulated sugar until the mixture is light and fluffy, about 3-5 minutes using an electric mixer.

Add the egg and vanilla extract, mixing until fully combined, ensuring a smooth texture before moving to the next step.

In a separate bowl, whisk together all-purpose flour, cornstarch, baking powder, and salt until evenly blended.

Gradually add the dry mixture to the wet ingredients, mixing on low speed just until combined, avoiding over-mixing.

Divide the dough into two equal portions and wrap each in plastic wrap. Chill in the refrigerator for at least 2 hours.

Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

On a lightly floured surface, roll out the chilled dough to about 1/3 inch thick and cut out circles using a cookie cutter.

Take the larger circles of dough and gently press the smaller circles onto the top edges to form the polar bear ears.

Arrange them on the prepared baking sheets and place them in the refrigerator for another 15 minutes.

Bake the cookies in the preheated oven for 12-14 minutes, or until lightly golden around the edges.

Allow the cookies to cool on the baking sheet for 15 minutes before transferring them to a wire rack to cool completely.

In a mixing bowl, beat together unsalted butter, powdered sugar, vanilla extract, salt, and heavy cream until smooth and fluffy.

Once the cookies have cooled completely, frost them generously with the buttercream frosting and decorate as desired.