In a medium bowl, whisk the flour, cornstarch, cocoa powder, and salt
Preheat oven to 350 degrees and line two cookie sheets with parchment paper or silicone mats
Using a standing mixer, beat the butter, cream cheese, and sugar until combined, smooth and fluffy
Beat in the egg yolk, vanilla, and red food coloring
Gradually beat in the dry ingredients until combined and a dough forms
Sprinkle flour onto a cutting board and roll the cookie dough to 1/4in thick
Cut out heart-shaped cookies and place them onto the cookie sheets
Bake in the oven for 12-14 minutes or until set around the edges
Remove and allow to cool completely
Using a standing mixer, beat the butter and vanilla until light in color
Gradually beat in the melted white chocolate
Beat in the powdered sugar until combined
Scoop the frosting into the disposable piping bag and cut the tip-off
Pipe an outline around the edge of the cookies
Fill in the center with the frosting and smooth with an angled spatula
Sprinkle some valentine's Day sprinkles on top
Allow the frosting to harden before enjoying the cookies!