Make the cookie dough: Beat butter and cream cheese together on medium speed until smooth. Add sugar and mix 2 minutes until light and fluffy. Beat in egg and vanilla until combined.

Combine dry ingredients: Whisk flour, cornstarch, baking powder, and salt in a separate bowl. Add gradually to the wet ingredients and mix on low until just combined. Dough will be sticky.

Chill dough: Divide dough in half, wrap in plastic, flatten to ½‑inch thick discs, and chill at least 2 hours or overnight.

Prepare for baking: Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone mats.

Shape cookies: Roll chilled dough on floured plastic wrap to ⅓‑inch thickness. Cut 2½‑inch circles for heads and ¾‑inch circles for ears. Attach ears gently by pressing edges together. Chill shapes for 15 minutes.

Bake: Bake 12–14 minutes on the top rack until just set and not browned. Cool cookies 15 minutes on the pan, then move to wire racks.

Make frosting: Beat butter, vanilla, and salt 30 seconds. Gradually add powdered sugar, then drizzle in cream until smooth and spreadable.

Decorate cookies: Spread or pipe frosting on cookies and press into sanding sugar for snowy texture. Pipe a small oval of frosting for the muzzle, add a chocolate chip for the nose, black sprinkles for eyes, and red or pink sprinkles for inner ears.