Start by sifting together all-purpose flour, cornstarch, and cocoa powder in a medium bowl; set aside. In a large mixing bowl, cream together softened unsalted butter, powdered sugar, and vanilla until smooth and fluffy. Add red food coloring and mix until evenly incorporated.

Gradually fold the dry flour mixture into the wet mixture, stirring gently. Mix until just combined, ensuring there are no dry patches. If the dough is too thick, adjust the consistency with a splash of milk until it reaches a thick but pipeable texture.

Using a piping bag fitted with a Wilton 2D tip, carefully pipe flower shapes onto a lined baking sheet, creating lovely rose designs. Once piped, refrigerate the cookies for 30-60 minutes to firm them up.

Preheat your oven to 170°C (340°F). Once ready, bake for 8-10 minutes until set but slightly soft to the touch. Let the cookies cool on the sheet for about 5 minutes before transferring them to a wire rack to cool completely.

Prepare the cream cheese filling by beating together softened cream cheese, additional unsalted butter, and vanilla extract until creamy. Gradually add powdered sugar, mixing until smooth and thick.

Once cookies are completely cool, pair them up and pipe or spread cream cheese filling on the bottom of one cookie and sandwich with another cookie on top.